High efficiency configuration for solar cell string.

(54) Title: HIGH EFFICIENCY CONFIGURATION FOR SOLAR CELL CHAIN.

(54) Title: HIGH EFFICIENCY CONFIGURATION FOR SOLAR CELL STRING.

(57) Summary

A high-efficiency configuration for a string of solar cells comprises series-connected solar cells arranged in a pattern of overlapping tejamanils. Front and back surface metallization patterns can provide additional increases in efficiency. Alternative sources of energy are needed to meet the world's increasing energy demands. Solar energy resources are sufficient in many geographic regions to meet such demands, in part, by providing the electrical energy generated by solar cells (eg, photovoltaics).

(57) Abstract

A high efficiency configuration for a string of solar cells comprises series-connected solar cells arranged in an overlapping shingle pattern. Front and back surface metallization patterns may provide further increases in efficiency. Alternate sources of energy are needed to satisfy ever increasing world-wide energy demands. Solar energy resources are sufficient in many geographical regions to satisfy such demands, in part, by provision of electric power generated with solar (eg, photovoltaic) cells.

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PATENT TITLE No. 347994

<td>Holders):</td><td>SUNPOWER CORPORATION</td>

<td>D micilio:</td><td>77 Río Robles, San José, California, 95134, USA</td>

<td>Denomination:</td><td>HIGH EFFICIENCY CONFIGURATION FOR SOLAR CELL CHAIN.</td>

<td>Classification:</td><td>CIP: H01L31 / 05; H01L31 / 00 CPC: H01L31 / 042; H01L31 / 044; H01L31 / 048; H01L31 / 0504; H01L31 / 0508; H02S40 / 36; Y02E10 / 50</td>

<td>Inventor (s):</td><td>RATSON MORAD; NATHAN P, BECKETT; JOHN ANTHONY GANNON; GILAD ALMOGY,</td>

REQUEST

<td>Number: MX / a / 2015/005844</td><td>International Presentation Date: 08deNpviembréde2013 PRIORITY* *</td>

<td>Country:</td><td>Date: Number:</td>

<td>US US Validity: Twenty years</td><td>November 8, 2012 13 / 672,386 December 6, 2012 61 / 734,239</td>

Expiration Date: November 8, 2033

Issue Date: May 22, 2017

The reference patent is granted based on the articles⁰, 2^or fractionV, 6 ° ί ^ βΗόή-Λ, and SS of the Industrial Property Law.

In accordance with article 23 of the Property Law Inctaeteaklaptesente patent bene a validity of twenty years, renewable from the date of filing the application / will be subject to the payment of the fee pafa-manterwwgeiites the rights.?

Whoever signs this title hweicdd it based on the provisions, by ios articles 6 · sections III and 7 ° bis 2 of the Industrial Property Law (Official Gazette of the Federation (OOF) 06/27/1991, amended on Q2 / 08/1994, 10/25/1996, 12/26/1997, 1.7 / 06/1999, 01/26/2004, 06/16/2005, 01/25/2006, 05/06/2009, 06 / 01/2010, 06/18/2010, 06/28/2010, 01/27/2012 and 04/09/2012), artanitas-1 °, Wraction V paragraph a), 4th and 12th sections I and III of the Regulations of the Mexican Institute of Industrial Property (DOF, 12/14/1999, amended on 07/01/2002, 07/16/2004, 07/28/2004 and 09/07 / 2007); Articles 1, 3, 4, 5 fraction V subsection a), 4βfraaraon0J ydll-y 30 of the Organic Statute 'of the Mexican Institute of Industrial Property (DOF 12/27/1999, amended 10/10/2002, 07/29/2008 ^ 04 / (180004 T * mBW20lW); ajudel Agreement that delegates powers to the Directors

Deputy Generals, Coordinator, DivaMalaa Directors, · Jftulaaai de «las * 0fí8ílee Regionals, Divisional Deputy Directors, Departmental Coordinators and other subordinates of the Instituto Mexidanonfe Industrial Property fnXXF. 12/15/1999, amended on 02/04/2000, 07/29/2004, 08/04/2004 and 09/13/2007).

This document is signed with an advanced electronic signature (FIEL), based on articles 7 BIS 2 of the Industrial Property Law; 3 of its Regulations, and 1 section III, 2 section V, 26 BIS and 26 TER of the Agreement establishing the guidelines for the use of the Payment and Electronic Services Portal (PASE) of the Mexican Institute of Industrial Property, in the procedures indicated.

DIVISIONAL PATENT DIRECTOR NAHANNY CANAL REYES

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Original string:

NAHANNY MARISOL CANAL REYES | 00001000000403252793 | Administration Service

Tax | 1695 || MX / 2017/40938 | MX / a / 2015/005844 | PCT patent title | 1220 | RRGO | Page (s) 2 | WS4dJgLgylkl7fqn7l7N3jLLdlY =

Digital stamp:

G7M5qRrovCRYCwhOJfbEzgeXdgyuP3aZqoUU / 7pfdJZsLfjKbfekt2Ze3g4horS2ikqgE8umV2h + NhBBvtfWvROjao gZXq1wCsfSSW8gbrNTwqME7cdEWV1NuQT0TRIs / nD3rmfgJ9QH6o0nWsu5ADTr5ebvE6d + W + CfqjgWxUwFC + r sfmZ2E k7JbWslbZDaegKxmXOPyueM6YmErlpRSzvtR0P / 9A3Ugrj1bvAzhdo0NhdYB92pQ / Yh7NKCcHLhM2S4D0nSC0llzTa w8HnwTgD poBRxWH8eykUA9xBpjduxF3FBK8BqZDchUr081PA9 + + + rVQ W1ytjZ7QxZnoXKBrr == * Additional Information to the back

Sand! No. 550, Floor 1, Pueblo Santa María Tepepan, Xochimilco. 16020, Mexico City (55) 53340700 www gob.mx/impi

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OF THE PUJ?! FDAO INDUSTRIAL

HIGH EFFICIENCY CONFIGURATION FOR CHAIN ​​^ DE — CgLDftS *

SOLAR

FIELD OF THE INVENTION

The invention generally relates to solar cells and their use in concentrating solar energy collectors.

BACKGROUND OF THE INVENTION

Alternative energy sources are needed to meet the world's increasing energy demands. Solar energy resources are sufficient in many geographic regions to meet such demands, in part, by providing electrical energy generated by solar cells (eg, photovoltaic).

BRIEF DESCRIPTION OF THE INVENTION

High efficiency solar cell arrangements are disclosed in this document. Solar cells and solar cell strings as disclosed in this document can be particularly valuable in concentrating photovoltaic systems, in which mirrors or lenses concentrate sunlight on a photovoltaic cell for light intensities greater than that of a solar cell. Sun.

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In one aspect, a solar cell comprises a silicon semiconductor diode structure having rectangular or substantially rectangular front and back surfaces having shapes defined by oppositely positioned first and second long sides of the solar cell and two oppositely positioned short sides of the solar cell. solar cell. In operation, the front surface is illuminated by light. The solar cell comprises an electrically conductive front surface metallization pattern positioned on the front surface. This metallization pattern includes a plurality of fingers that run parallel to the short sides of the solar cell for substantially the length of the short sides. An electrically conductive back surface metallization pattern is placed on the back surface.

In some variations, the front surface metallization pattern does not include a bus bar that interconnects the fingers to pick up current from the front surface of the solar cell. In such variations, the back surface metallization pattern may lack any conventionally prepared contact pads for solder connections to the solar cell. Alternatively, the back surface metallization pattern may include, for example, a

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INO'IMAL CONCLUSION PAD positioned adjacent. which runs parallel to a long side of the solar cell for substantially the length of the long side, or two or more discrete contact pads positioned adjacent and arranged parallel to the long side.

In some variations, the front surface metallization pattern comprises only a single busbar, which is positioned adjacent and runs parallel to the first long side for substantially the length of the first long side. The fingers of the front metallization pattern are attached to and interconnected by means of the bus bar. In such variations, the back surface metallization pattern may be devoid of any contact pads. Alternatively, the back surface metallization pattern may include, for example, one contact pad positioned adjacent and running parallel to the second long side for substantially the length of the second long side, or two or more discrete contact pads positioned adjacent and accommodated parallel to the second long side. These contact pads can have widths measured perpendicular to the long sides that roughly match the width of the busbar, for example. In any of these variations, the Mexican &lt;IMPI ^ ϊΗττττυτο pattern

Dí LA FtOPIETAD metallization of front surface can include shunt that has perpendicular width ^ i * ΰ dL! éje Id'f ^ l? Narrower than the width of the busbar and interconnecting two or more fingers to provide multiple current paths from each of the two or more interconnected fingers to the busbar. The bypass conductor can be positioned adjacent and run parallel to the bus bar, for example.

In some variations, the front surface metallization pattern comprises two or more discrete contact pads positioned adjacent the first long side. Each of the fingers of the front metallization pattern is electrically bonded and connected to at least one of the contact pads. In such variations, the back surface metallization pattern may be devoid of any contact pads. Alternatively, the back surface metallization pattern may include, for example, one contact pad positioned adjacent and running parallel to the second long side for substantially the length of the second long side, or two or more discrete contact pads positioned adjacent and accommodated parallel to the second long side. These contact pads can have widths measured perpendicular to the long sides that fit

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example. In either of these variations, the front surface metallization pattern may include a shunt conductor that has a perpendicular width as well as length narrower than the widths of the front surface metallization contact pads and that interconnects two or more fingers to provide multiple current paths from each of the two or more interconnected fingers to one or more of the contact pads.

In any of the above variations, the solar cell can comprise any suitable silicon semiconductor diode structure. For example, the solar cell may comprise an intrinsic thin layer heterojunction (HIT) structure.

In any of the above variations, the ratio of the length of a long side of the solar cell relative to the length of a short side of the solar cell can be greater than or equal to about three, for example.

A concentrating solar energy collector can comprise the solar cell of any of the previous variations and one or more optical elements arranged to ₆ IMPI

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, industrial concentrating solar radiation on the solar cell.

,,,,, - In another aspect, a string of solar cells comprises at least a first silicon solar cell and a second silicon solar cell. The first silicon solar cell comprises a front surface to be illuminated by light, a rear surface, and an electrically conductive front surface metallization pattern positioned on the front surface. The second silicon solar cell comprises a front surface to be illuminated by the light, a rear surface, and an electrically conductive rear surface metallization pattern positioned on the rear surface. The first and second solar cells are positioned with one edge of the rear surface of the second silicon solar cell overlapping an edge of the front surface of the first silicon solar cell. A portion of the front surface metallization pattern of the first silicon solar cell is hidden by the second silicon solar cell and a portion of the rear surface metallization pattern of the second silicon solar cell is bonded with a bonding material. electrically conductive to electrically connect the first and second silicon solar cells in series.

Either or both of the first and second silicon solar cells can be, for example, any of

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IMSTrTVTO MBUCAM .;

D * U PSOPIEDAP INDIVIDUAL

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the variations of the silicon solar cell outlined above. In such variations, the overlapping edges of the silicon solar cells can be defined by long sides of the solar cells, for example, and the edges can be arranged parallel to each other. If the front surface metallization pattern of the first silicon solar cell includes a bypass conductor, the bypass conductor may be hidden, or not hidden, by the second silicon solar cell.

The first and second solar cells may be joined together at the overlapping portions of the solar cells with an electrically conductive solder. As an alternative to soldering, solar cells can rather be bonded together with, for example, an electrically conductive film, an electrically conductive paste, an electrically conductive epoxy (eg, an electrically conductive silver epoxy) , an electrically conductive tape, or other suitable electrically conductive adhesive. These alternatives to soldering can be selected, for example, to provide more mechanical compliance than would be provided by means of an electrically conductive solder joint. The electrically conductive bonding material that joins the solar cells together can also interconnect fingers of the _ IMPIOS pattern.

MEXICAN INSTITUTE

PE UA FICHEDAD &lt;INDUSTRIAL metallization of front surface to carry out the current collection function of a bus bar. The front surface metallization pattern in solar cells may therefore lack any bus bars.

A concentrating solar energy collector may comprise the string of solar cells of any of the above variations and one or more optical elements arranged to concentrate the solar radiation on the string.

In another aspect, a solar energy receiver comprises a metal substrate and a series connected chain of two or more solar cells positioned on the metal substrate with the ends of adjacent solar cells overlapping in a shingle pattern. Adjacent superposed pairs of solar cells can be electrically connected in a region where they overlap by means of an electrically conductive junction between the front surface of one of the solar cells and the rear surface of the other solar cell. The electrically conductive bond may be between a metallization pattern on the front surface of one solar cell and a metallization pattern on the rear surface of the other solar cell, for example. Solar cells can be, for example, silicon solar cells, including any of the silicon solar cell variations outlined above ^ Tr'TúT ^ i'qttTerra * - * the back-contact silicon solar cell variations described below , or solar cells configured in a similar way to any of those variations, but that use another system of material different or in addition to silicon. The electrically conductive junction between the solar cells can be formed, for example, by any of the methods outlined above. Solar cells can be placed in a lamination stack that sticks to the metal substrate, for example.

In some variations, the metal substrate is linearly elongated, each of the solar cells is linearly elongated, and the string of solar cells is arranged in a row along a long axis of the metal substrate with the long axes of the Solar cells oriented perpendicular to the long axis of the metal substrate. This row of solar cells may be the only row of solar cells on the substrate.

In some variations, the series-connected string of solar cells is a first string of solar cells, and the solar energy receiver comprises a second string-connected string of two or more solar cells accommodated with

<img file="MX347994B_D0008.tif" />

the ends of the solar cells overlapping in a shingle pattern. The second string of solar cells is also placed on the metal substrate. A mechanically formed electrical interconnect can electrically couple the rear surface of a solar cell at one end of the first string of solar cells to the front surface of a solar cell at one end of the second string of solar cells. The interconnection can be between a metallization pattern on the front surface of one solar cell and a metallization pattern on the rear surface of the other solar cell, for example. The solar cell at the end of the first solar cell string may overlap the solar cell at the end of the second solar cell string and hide the mechanically formed electrical interconnect from view from the front (illuminated) surface side of the solar cells. In such variations, the metal substrate can be linearly elongated, each of the solar cells can be linearly elongated, and the first and second strings of solar cells can be arranged in line in a row along a long axis of the substrate. metal with the long axes of the solar cells oriented perpendicular to the long axis of the metal substrate.

A concentrating solar energy collector may comprise the solar energy receiver of any of the previous variations and one or more optical elements arranged to concentrate the solar radiation on the receiver.

In another aspect, a string of solar cells comprises a first group of solar cells arranged with the ends of adjacent solar cells overlapping in a shingle pattern and connected in series by means of electrical connections between solar cells made in the overlapping regions of adjacent solar cells, a second group of solar cells arranged with the ends of the adjacent solar cells overlapping in a shingle pattern and connected in series by means of electrical connections between solar cells made in the overlapping regions of the adjacent solar cells, and a shaped electrical interconnection mechanically that electrically couples the first group of solar cells to the second group of solar cells in series. The mechanically formed electrical interconnect can electrically couple the rear surface of a solar cell at one end of the first group of solar cells to a front surface of a solar cell at one end of the second group of solar cells, for example. The interconnection can be between a¹² Mexican ηχπττυτο „, 4. , __ 4 .. '_ 1 _ „„ -C ___ metallization pattern on the front surface' Nuds' iAiina^{&gt; e}"If" a solar and a metallization pattern in the s-upe ^ Tgi-e-'piygteriσι of the other solar cell, for example. The mechanically formed electrical interconnect can be attached to solar cells with electrically conductive junctions made by any of the methods outlined above, for example.

The solar cells can be, for example, silicon solar cells, including any of the variations of silicon solar cells outlined above or any of the variations of back-contact silicon solar cells described below, or solar cells configured in such a manner. similar to any of these variations but using a different material system or in addition to silicon. Electrical connections between overlapping solar cells can be made, for example, with electrically conductive junctions made by any of the methods outlined above.

In such variations, a space between the two groups of solar cells where they are interconnected by means of the mechanically formed electrical interconnect may be less than or equal to about five millimeters in width, for example. Also in such variations, the mechanically formed electrical interconnect may comprise a slat

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metal oriented perpendicular to a long axis of the row of solar cells and electrically coupled to a rear surface of a solar cell at one end of the first group of solar cells and to a front surface in a solar cell at one end of the second group of cells solar.

The electrical interconnect mechanically formed in any of the above variations may comprise a patterned metal slat with slits or openings, for example, to increase its mechanical conformation.

In any of the above variations, the solar cell at the end of the first group of solar cells can overlap the solar cell at the end of the second group of solar cells and hide the mechanically formed electrical interconnect from view from the front surface side. of the solar cell chain.

A concentrating solar energy collector may comprise the string of solar cells of any of the above variations and one or more optical elements arranged to concentrate the solar radiation on the string.

In another aspect, a string of solar cells comprises at least a first solar cell and a second solar cell. The first solar cell comprises a front surface to be

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<img file="MX347994B_D0010.tif" />

illuminated by light, a ______ back surface, and (optionally) an electrically conductive front surface metallization pattern placed on the front surface. The second solar cell comprises a front surface to be illuminated by light, a rear surface, and an electrically conductive rear surface metallization pattern positioned on the rear surface. The string of solar cells also comprises at least a first mechanically shaped electrical interconnection. The first and second solar cells are positioned with an edge of the rear surface of the second solar cell overlapping an edge of the front surface of the first solar cell. The mechanically formed electrical interconnect is attached to a portion of the front surface of the first solar cell that is hidden by the second solar cell and attached to a portion of the rear surface of the second solar cell to electrically connect the first and second cells. solar in series. In this arrangement, the second solar cell hides the mechanically formed electrical interconnect from the front surface side of the first solar cell from view. The interconnection can be between a metallization pattern on the front surface of a solar cell and a metallization pattern on the rear surface.

<img file="MX347994B_D0011.tif" />

from the other solar cell, for example.

Either or both of the first

IMPI ^{, NST}mexican nyro ^ΠΕ THE FROHEDAD tuamui and second solar cells can be, for example, any of the variations of silicon solar cells outlined above or any of the variations of back-contact silicon solar cells described below, or solar cells configured similarly to any of these variations but using a different material system or in addition to silicon. In such variations, the overlapping edges of the silicon solar cells can be defined by long sides of the solar cells, for example, and the edges can be arranged parallel to each other. If the first solar cell comprises a front surface metallization pattern that includes a bypass conductor, the bypass conductor may be hidden, or not hidden, by the second solar cell.

The mechanically formed electrical interconnect can be attached to solar cells with electrically conductive junctions made by any of the methods outlined above, for example. Electrically conductive junctions can interconnect fingers of a front surface metallization pattern on the first solar cell, if present, to perform the pickup function

<img file="MX347994B_D0012.tif" />

current from a busbar. A front surface metallization pattern on the solar cell may therefore lack any bus bars.

The mechanically formed electrical interconnect may comprise, for example, a flat metal strip, a bent metal strip, or a spoken metal strip to form a circuit. The mechanically formed electrical interconnect may comprise a patterned metal slat to enhance its mechanical conformation.

The solar cell string may comprise a second mechanically formed electrical interconnect and a third solar cell having a front surface to be illuminated by light, a back surface, and an electrically conductive back surface metallization pattern positioned on the back surface. The second and third solar cells are positioned with one edge of the rear surface of the third solar cell overlapping an edge of the front surface of the second silicon solar cell. The mechanically formed electrical interconnect is attached to a portion of the front surface of the second solar cell that is hidden by the third solar cell and attached to a portion of the rear surface of the third solar cell to electrically connect the second and third cells. solar in series.

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The interconnection can be between a metallization pattern on the front surface of the second solar cell and a metallization pattern on the rear surface of the third solar cell, for example. The mechanically formed electrical interconnect can be attached to the solar cells with electrically conductive joints made by any of the methods outlined above, for example. The electrically conductive junctions can interconnect fingers of a front surface metallization pattern of the second solar cell to perform the current pickup function of a bus bar. A front surface metallization pattern on the solar cell may therefore lack any bus bars.

A concentrating solar energy collector may comprise the string of solar cells of any of the above variations and one or more optical elements arranged to concentrate the solar radiation on the string.

In another aspect, a solar energy receiver comprises a substrate, a thermally conductive encapsulating layer that adheres to the substrate, a string of solar cells placed in the thermally conductive encapsulating layer, a transparent encapsulating layer placed in the solar cell string, and a transparent topsheet attached

<img file="MX347994B_D0013.tif" />

thermally conductive comprises pigments. The solar cTTTTTS can be, for example, any of the variations of silicon solar cells outlined above or any of the variations of back-contact silicon solar cells described below, or solar cells configured similarly to any of those. variations but using a different material system or in addition to silicon.

The thermally conductive encapsulating layer can reflect a substantial portion of the solar radiation incident thereon. In such variations, the thermally conductive encapsulating layer can be white, for example. Furthermore, in such variations, the solar cells may be HIT solar cells, with the reflective encapsulating layer accommodated to reflect unabsorbed radiation through the HIT cell to the reflective layer to the HIT solar cell. Alternatively, the thermally conductive encapsulating layer can absorb a substantial portion of incident solar radiation thereon. In such variations, the thermally conductive encapsulating layer can be black, for example. The transparent topsheet can have a moisture transmission rate less than or equal to about 0.01₁₉ and ΙΝίΤΠΤΓΓΟ MEXICANO JR

OS THE MOPISTY LXy

INDmwrAl grams per meter-day, for example. The solar cell string may comprise a plurality of arranged solar cells with adjacent solar cell ends overlapping in a shingle pattern.

A concentrating solar energy collector may comprise the solar energy receiver of any of the previous variations and one or more optical elements arranged to concentrate the solar radiation on the receiver.

In another aspect, a back contact silicon solar cell comprises a front surface to be illuminated by light, a back surface, one or more n contacts on the back surface electrically contacting an n-type conductivity side of a diode junction. of silicon, one or more p contacts on the back surface electrically contacting a p-type conductivity side of the silicon diode junction, and one or more electrically conductive paths. The electrically conductive pathway passes through the solar cell from the rear surface to the front surface to provide, near an edge of the front surface, one or more electrical connections to any of the po contacts.

The front and rear surfaces may have corresponding substantially rectangular shapes

INSTITUTO MIXICano βΕ ΙΑ rROPULAf. IN &amp; USTRIAl rectangular defined by two oppositely positioned long sides and two oppositely positioned short sides, with upper ends of the tracks arranged along one long side of the front surface. In some such variations, the contacts n comprise a plurality of fingers n arranged side by side and running parallel to the short sides of the rear surface, the contacts p comprise a plurality of fingers p arranged side by side and running parallel to the short sides of the posterior surface, and the n and p fingers are interdigitated. In other variations, the contacts n comprise a plurality of fingers n arranged side by side and running parallel to each other at an angle with respect to the short sides of the rear surface such that the opposite ends of each finger n are out of phase. in a direction parallel to the long sides by a distance equal to a step distance between fingers n, the contacts p comprise a plurality of fingers p arranged side by side and running parallel to each other at an angle with respect to the short sides of the rear surface such that the opposite ends of each finger p are out of phase in a parallel direction to the long sides by a distance equal to a step distance between fingers p, and fingers n and fingers p are interdigitated.

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In other variations, the upper ends ^^^ Óe pathways may be arranged along a lad ^^ oTT ^ '^^ · * ·· front surface, and the fingers n and the fingers p may be similarly configured as outlined above except that they run parallel to, or at an angle to, the long sides of the back surface. In still other variations, the back contact solar cell can be substantially square, with vias and fingers arranged in a similar manner as outlined above and running parallel to, or at an angle to, a pair of sides of the solar cell. .

In any of the above variations, the rear contact solar cell may comprise a bus bar or a plurality of contact pads on the front surface that electrically interconnect the upper ends of the tracks.

A concentrating solar energy collector may comprise the solar cell that back contact from any of the above variations and one or more optical elements arranged to concentrate the solar radiation on the solar cell.

In another aspect, a string of solar cells comprises a first rear contact silicon solar cell comprising a front surface to be illuminated by light,

<img file="MX347994B_D0014.tif" />

₂₂ IMPI

MEXICAN INSTITUTE

OF THE FWFIEDAD

INDUSTRIAL one back surface, one or more n back surface contacts electrically contacting an n-type conductivity side of a diode junction, one or more p-contacts on the back surface electrically contacting a p-type conductivity side of the diode junction , and a second rear contact silicon solar cell comprising a front surface illuminated by light, a rear surface, one or more n contacts on the back surface electrically contacting an n-type conductivity side of a diode junction, and one or more p contacts on the back surface electrically contacting a p-type conductivity side of the diode junction. The first and second back contact silicon solar cells are positioned with one edge of the back surface of the second back contact silicon solar cell overlapping one edge of the front surface of the first back contact silicon solar cell and are electrically connected in series.

The back-contact silicon solar cells can be, for example, any of the back-contact silicon solar cell variations outlined above.

In some variations, the first rear contact silicon solar cell comprises one or more pathways

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²³ IMPI tNsTTivrc Mexican r&gt; F LA ΡβΓΚΕΟΑΓ. electrically conductive that pass through solar from its surface posterior to its supe? fr5T ^ “fTOnTa ^^ to electrically interconnect any of the contacts po the contacts n of the first rear contact silicon solar cell to the opposite polarity contacts in the rear surface of the second rear contact silicon solar cell. The upper ends of the conduction pathways can be located, for example, in a region of the front surface of the first rear contact silicon solar cell overlapping by the second rear contact silicon solar cell. The conduction paths can be electrically connected to the contacts on the rear surface of the second silicon solar cell by one or more electrically conductive junctions between the front surface of the first rear contact silicon solar cell and the rear surface of the second. back contact silicon solar cell. Electrically conductive joints can be made by any of the methods outlined above, for example. The first rear contact silicon solar cell may optionally comprise a bus bar or a plurality of contact pads on its front surface which electrically interconnect the upper ends of the pathways with each other, and which connect

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IN Γ * »STW 1Λ lq ^ -¹ S »electrically to the contacts on the rear surface of the second rear contact silicon solar cell by said one or more electrically conductive junctions.

In other variations, a mechanically formed electrical interconnect electrically connects any of the po contacts on the back surface of the first rear contact silicon solar cell to the opposite polarity electrical contacts on the back surface of the second silicon solar cell. back contact silicon. The mechanically formed electrical interconnect can be attached to the solar cells with electrically conductive joints made by any of the methods outlined above, for example.

A concentrating solar energy collector may comprise the solar cell string of any of the variations described above and one or more optical elements arranged to concentrate the solar radiation on the solar cell.

In another aspect, a solar energy receiver comprises a substrate, and a series connected string of two or more solar cells positioned on the substrate with adjacent solar cell ends overlapping in a shingle pattern. The linear coefficient of thermal expansion of the solar cells differs with respect to that of the substrate in an as IMPIAS ίΝτπτυτο mlucanv »

DF LA FROMlDAb

BIBUSTRIAl - value greater than or equal to approximately 5 χ 10, or greater than or equal to approximately 10. χ i 0 ~^ύ, or a value greater than or equal to approximately 15 χ 10 '⁶, or a value greater than or equal to approximately 20 χ 10 ~⁶.

Solar cells can be silicon solar cells, for example. Solar cells can be, for example, any of the variations of silicon solar cells outlined above, including variations of HIT and back-contact silicon solar cells, or solar cells configured similarly to any of those variations but using another system of different material or in addition to silicon.

The adjacent superposed pairs of solar cells in the string may be connected in series in a region where they overlap by an electrically conductive junction between a front surface of one of the solar cells and a rear surface of the other solar cell. Such electrically conductive bonds can be formed by any of the methods outlined above, for example. Alternatively, adjacent superposed pairs of solar cells may be electrically connected in series in a region where they overlap by a mechanically formed electrical interconnect between a front surface of one of the solar cells and a rear surface of the other cell.⁰Formed electrical interconnections, ap amon tc, can join solar cells with electrically conductive junctions made by any of the methods outlined above, for example.

The substrate can be a metal substrate, an example. The substrate can be an aluminum substrate, for example.

In some variations, the metal substrate is linearly elongated, each of the solar cells is linearly elongated, and the string of solar cells is arranged in a row along a long axis of the substrate with the long axes of the solar cells. oriented perpendicular to the long axis of the substrate. In such variations, the string of solar cells may be a first string of solar cells, and the solar energy receiver may also comprise a second string connected in series of two or more solar cells placed on the substrate with adjacent solar cell ends overlapping. in a shingle pattern, and a mechanically formed electrical interconnect that electrically connects the first and second strings in series. The linear coefficient of thermal expansion of solar cells in the second chain can also differ from that of the substrate by a value greater than or equal to approximately 5 χ 1CT⁶, or in a greater or equal value greater or equal value

7 that approximately that approximately

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x 10 ⁶, or a value greater than or equal to approximately 20 ^x 10 ⁶. The second chain can be positioned in line with the first chain. The overlapping pairs of solar cells in the second string can be bonded to each other or otherwise interconnected as outlined above for the first string, for example.

A concentrating solar energy collector may comprise the solar energy receiver of any of the variations outlined above and one or more optical elements arranged to concentrate solar radiation on the receiver.

In another aspect, a method of laminating solar cells to a substrate comprises accommodating a plurality of solar cells to form a series connected string of solar cells with adjacent solar cell ends overlapping in a shingle pattern, placing the solar cell string in a stack of layers on the substrate, and apply a pressure no greater than about 0.6 atmospheres to force the stack of layers and substrate together. The pressure can be, for example, less than or equal to about 0.4 atmospheres. The pressure can be, for example, between about 0.2 and 0.6 atmospheres. He

IWSTTTVTO MEXICANO DE LA MOHEDAL method may comprise heating the substrate, ινπ '^ ιαι pr? ^ = - of layers, or the substrate and the stack of layers h &lt;T ^ / 3. “UTI'JΐδΠφΤ'ΓΗ'ί'ϋΤΗ de between approximately 130 ° C and 160 ° C while applying pressure. This method can be used with any of the variations of solar cells, and any of the variations of superimposed series connected solar cell strings, outlined above.

In another aspect, a method of preparing a string of solar cells comprises accommodating a plurality of solar cells with adjacent solar cell ends overlapping in a shingle fashion and with an uncured electrically conductive epoxy positioned between the overlapping portions of adjacent solar cells. at selected locations to daisy chain solar cells. The method also comprises applying pressure to force the overlapping ends of the solar cells against each other while raising a temperature of the solar cells to cure the electrically conductive epoxy to form electrically conductive bonds between the solar cells. In some variations, after the electrically conductive epoxy is cured, the solar cell string is placed in a stack of layers on a substrate which is then laminated to the substrate. In other variations, the string of solar cells is placed in a stack of layers on a substrate ₂₉ IMPI ^ ΐΝίττη / Mexican το 'Ce-Sí · », .-:

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INDUSTRIAL ~ ^ cT-V before electrically conductive epoxy cures.

The stack is then laminated to the substrate. Electrically conductive epoxy cures (under pressure) during the lamination process. This method can be used with any of the solar cell variations outlined above.

In any of the overlapping solar cell strings outlined above, the amount of overlap between adjacent solar cells can vary along the string such that the size of the front surface area of ​​each solar cell that is not overlapped by a Adjacent cell varies through the string in a way that adjusts with the electrical performance of the solar cells. For example, the different sizes of illuminated area (that is, not overlapping) for each solar cell can be selected to compensate for the inherent performance differences between the cells in order to adjust with the current output for each cell when they are low equal. illumination.

Any of the superimposed solar cell chains outlined above can be positioned for operation in a solar energy collector with the chain oriented in such a way that for each solar cell that has a portion of its front surface superimposed by another solar cell, the

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front surface portion superimposed equator of the earth than the covered surface portion — fx-QjaXaJ_hq. With the string in this orientation, the exposed edges of the top overlapping solar cells are oriented away from the earth's equator.

Any of the silicon solar cell variations outlined above can be formed from one comprising, for example, monocrystalline or polycrystalline silicon.

These and other embodiments, features and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following more detailed description of the invention in conjunction with the accompanying drawings which are first briefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A shows a schematic diagram of an exemplary front surface metallization pattern for a solar cell.

Figure IB shows a schematic diagram of an exemplary back surface metallization pattern that can be used, for example, for a solar cell having the front surface metallization pattern of the

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Figure 1C shows a schematic diagram of an exemplary back surface metallization pattern for a back contact solar cell in which the contacts on both sides of the diode junction are made on the back surface and in which the vias pass to through the cell from the rear surface to the front surface to provide electrical connection at an edge of the front surface to one side of the diode junction.

Figure ID shows an exemplary front surface metallization pattern for a back contact solar cell in which vias pass through the cell from the back surface to the front surface to provide electrical connections from one side of the diode junction. to a busbar along one edge of the front surface.

Figure 1E shows a perspective view of an exemplary back contact solar cell employing the front surface and exemplary back surface metallization patterns of Figure 1C and Figure ID, respectively.

Figure 1F shows another exemplary back surface metallization pattern for a back contact solar cell in which the contacts on both sides of ₃₂ w^pw

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Figure 2 shows a fragmentary view schematically illustrating one end of a solar energy receiver comprising a string of serially connected solar cells arranged in an overlapping manner on a linearly elongated substrate. Each solar cell has the front surface metallization pattern illustrated in Figure 1A.

Figure 3A shows a schematic cross-sectional diagram illustrating the overlap of adjacent solar cells in the string of solar cells shown in Figure 2.

Figure 3B shows a schematic cross-sectional diagram illustrating the overlap of adjacent back contact solar cells, with an electrical interconnection between the back surfaces of the overlapping solar cells made with a flexible electrical interconnect.

Figure 4 shows a schematic diagram of an exemplary solar cell string that includes a first group

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Figure 5A shows a schematic diagram of the exemplary mechanically formed interconnect used in the solar cell string illustrated in Figure 4.

Figure 5B shows a schematic diagram of another exemplary mechanically shaped interconnect that can be used, for example, in place of the interconnect shown in Figure 5A.

Figures 6A-6C show schematic cross-sectional diagrams illustrating additional examples of series connected strings of superposition solar cells.

Figures 7A and 7B show front and rear views, respectively, of another exemplary serially connected string of superimposed solar cells.

Figures 8A and 8B show front and rear views, respectively, of another exemplary serially connected string of superimposed solar cells.

Figure 9 shows a rear view of another exemplary series connected string of superimposed solar cells.

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Figure 10 shows a fragmentary schematic diagram of an e ^ Miplar lamination stack, comprising solar cells, placed in and adhered to a substrate.

Figure 11 shows a schematic diagram of an exemplary bypass diode flex circuit that can be employed, for example, with solar cells in a shingle fashion as described in this specification.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description should be read with reference to the drawings, in which identical reference numerals refer to similar elements throughout the different figures. The drawings, which are not necessarily to scale, represent selective embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one of skill in the art to make and use the invention, and describes various embodiments, adaptations, variations, alternatives, and uses of the invention, including what is currently believed to be the best way to carry out the invention. invention.

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As used in this specification · ίy ·&gt; ί .-। i niri yi appended claims, singular forms one, one, and the include plural references unless the context clearly indicates otherwise. Also, the term "parallel" is intended in the sense of parallel or substantially parallel and encompasses minor deviations from parallel geometries rather than requiring that any parallel arrangement described herein be exactly parallel. The term perpendicular is intended in the sense of perpendicular or substantially perpendicular and to encompass minor deviations from perpendicular geometries rather than requiring that any perpendicular arrangement described herein be exactly perpendicular.

This specification discloses high-efficiency configurations for strings of solar cells as well as solar cells (eg, photovoltaic cells), and electrically conductive interconnects for solar cells, that can be used in such strings. As further described below, high efficiency configuration strings can be conveniently employed in concentrating solar energy collectors in which solar radiation is concentrated onto solar cells with reflectors, lenses, or other optical components. Such collectors can concentrate light onto solar cells to provide illumination.

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INDUSTRIAL greater than or equal to approximately seven soles, for example.

Figure 1A shows a schematic diagram of an electrically conductive front surface metallization pattern on the front surface of an exemplary solar cell 10. The front surface of solar cell 10 is rectangular or substantially rectangular. Other shapes can also be used, as appropriate. The front surface metallization pattern includes a busbar 15 positioned adjacent to the edge of one of the long sides of the solar cell 10 and running parallel to the long sides for substantially the length of the long sides, and fingers 20 attached perpendicular to the busbar and running parallel thereto and with respect to the short sides of the solar cell 10 for substantially the length of the short sides.

Solar cell 10 comprises a semiconductor diode structure in which the front surface metallization pattern is placed. A back surface metallization pattern is placed on a back surface of solar cell 10 as shown, for example, in Figure IB and described below. The semiconductor structure may be, for example, a conventional crystalline silicon diode structure comprising an np junction, with the upper semiconductor layer on which the

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Referring now to Figure IB, an electrically conductive back surface metallization pattern on the back surface of solar cell 10 comprises back contact 25, and back contact pad 30 positioned adjacent the edge of one of the long sides of solar cell 10 and running parallel to the long sides for substantially the length of the long sides. Figure IB shows the rear side of solar cell 10 as viewed through the front surface of solar cell 10. As shown by a comparison of Figure IA and Figure IB, rear contact pad 30 and the front surface busbar 15 is positioned along opposite long sides of the solar cell 10. '

The front and back surface metallization patterns on the solar cell 10 provide electrical contacts to the semiconductor diode structure by means of which the electrical current generated in the solar cell 10, when illuminated by light, can provide a charge. external. Furthermore, the metallization patterns of

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OF LA FABNEDAJL · front and rear surfaces shown allow two such solar cells 10 to be positioned in an overlapping geometry with their long sides parallel to each other and with the rear contact pad 30 of one of the solar cells overlapping and physically and electrically connected to the front surface busbar 15 of the other solar cell. As further described below, this pattern can be continued, in a similar shingle fashion on a roof, to build a chain of two or more superimposed solar cells 10 electrically connected in series. Such an arrangement is hereinafter referred to as, for example, superimposed solar cells connected in series.

The exemplary solar cell 10 illustrated has a length of approximately 156 millimeters (mm), a width of approximately 26 mm, and therefore an aspect ratio (length of short side / length of long side) of approximately 1: 6 . Six such solar cells can be prepared on a standard 156mm x 156mm dimension silicon wafer, then separated (diced) to provide the solar cells as illustrated. In other variations, eight solar cells 10 having dimensions of approximately 19.5mm x 156mm, and therefore an aspect ratio of approximately 1: 8, can be prepared to

<img file="MX347994B_D0020.tif" />

start from a standard silicon wafer. More generally, solar cells 10 have aspect ratios of, for example, about 1: 3 to 1:20 and can be prepared from wafers of standard size or from wafers of any other suitable dimension. As explained further below, solar cells having long and narrow aspect ratios, as illustrated, can be conveniently employed in concentrating photovoltaic solar energy collectors in which solar radiation is concentrated onto the solar cells.

Referring again to Figure IA, in the illustrated example the front surface metallization pattern on solar cell 10 also comprises an optional bypass conductor 40 which runs parallel to and spaced from busbar 15. Bypass conductor 40 interconnects fingers 20 to electrically bypass cracks that may form between bus bar 15 and bypass conductor 40. Such cracks, which can cut fingers 20 at locations near busbar 15, can otherwise isolate regions of solar cell 10 from busbar 15. The bypass conductor provides an alternate electrical path between such cut fingers and the busbar. A bypass conductor 40 may have a width, for

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For example, less than or equal to about 1mm, less than or equal to about 0.5mm, or between about 0.05mm and 0.5mm. The illustrated example shows a bypass conductor 40 positioned parallel to busbar 15, extending the full length of busbar, and interconnecting each finger 20. This arrangement may be preferred, but not required. If present, the bypass conductor does not need to run parallel to the bus and does not need to extend the full length of the bus. Furthermore, a bypass conductor interconnects at least two fingers, but does not need to interconnect all the fingers. Two or more short shunt leads can be used instead of one longer shunt lead, for example. Any suitable arrangement of drop leads can be used. The use of such shunt conductors is described in greater detail in U.S. Patent Application Serial No. 13 / 371,790, entitled Solar Cell With Metallization Compensating For Or Preventing Cracking. Prevents Cracking), and filed on February 13, 2012, which is incorporated herein by reference in its entirety.

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The exemplary front surface metallization pattern of Figure 1A also includes an optional end conductor 42 that interconnects fingers 20 at its far ends, opposite busbar 15. The width of conductor 42 may be approximately the same as that of a finger 20, for example. Conductor 42 interconnects fingers 20 to electrically bypass cracks that may form between bypass conductor 40 and conductor 42, thereby providing a current path to bus bar 15 for regions of solar cell 10 than otherwise. shape could be electrically isolated by such cracks.

The bus bar 15, fingers 20, bypass conductor 40 (if present), and end conductor 42 (if present) of the front surface metallization pattern may be formed, for example, from silver which is conventionally used for such purposes and deposited, for example, by means of conventional screen printing methods. Alternatively, these features can be formed from electroplated copper. Any other suitable materials and processes can also be used. The busbar 15 may have a width perpendicular to its long axis of, for example, less than or equal to about 3₄₂ muucano institute - -c

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INDUSTHIAI mm, and in the illustrated example it has a width of about 1.5 mm. Fingers 20 may have widths, for example, from about 10 microns to 100 microns. In the illustrated example, the front surface metallization pattern includes approximately 125 fingers evenly spaced along the ~ 154mm length of busbar 15. Other variations may employ, for example, less than about 125, about 150, about 175, about 200, about 225, about 125 to about 225, or more than about 225 fingers evenly spaced along a bus bar 15 of about the same length (~ 154 mm. Generally, the width of the busbar and the width, number, and spacing of the fingers can be varied depending on the intensity of the solar radiation to be concentrated on the solar cell. Generally, higher concentrations of solar radiation on the solar cell require more fingers and / or wider fingers to accommodate the resulting higher current generated in the solar cell. In some variations, the fingers may have widths that are greater near the bus bar than they are away from the bus bar.

<img file="MX347994B_D0021.tif" />

Referring again to the exemplary back surface metallization pattern in Figure IB, the back contact 25 may be a conventionally deposited aluminum contact, for example, and can substantially cover the back surface of the solar cell 10. Alternatively, the back contact 25 can leave islands or other portions of the rear surface of solar cell 10 unmetallized. As yet another alternative, the rear contact 25 may comprise fingers similar to those in the front surface metallization pattern, which run parallel to each other and to the short sides of the solar cell 10 for substantially the length of the short sides. Any other suitable configuration for the rear contact 25 can also be used. The back contact pad 30 can be formed, for example, from silver paste which is conventionally used for such purposes and deposited, for example, by means of conventional screen printing methods. Alternatively, the contact 25 and / or the back contact pad 30 can be formed from electroplated copper. Any other material and process can also be used to form the back contact 25 and the back contact pad 30. The contact pad 30 must have a width perpendicular to its long axis of, for example, less than or equal to about 3 mm, and in the illustrated example it has a width of approximately 2mm. The rear contact pad 30 may have a width, for example, that approximately matches or matches the width of the front bus bar 15. In such cases, the rear contact pad 30 may have a width, for example, approximately 1 to 3 times the width of the bus bar 15.

The solar cells 10 may be Heterojunction with Intrinsic Thin Layer (HIT) silicon solar cells. In such cases, the HIT cells may employ, for example, the front surface metallization patterns described above with respect to Figure 1A or any variation of those front surface metallization patterns described herein. HIT cells may employ, for example, the back surface metallization patterns described above with respect to Figure IB or any variation of those back surface metallization patterns described herein. The back surface metallization pattern of the HIT cell may comprise fingers (e.g. silver fingers) similar to those in the front surface metallization pattern.

- IMPIAS Mexican iwmnho J. , _. „. ,,,, of Figure 1A. In such cases, the back surface metallization fingers can be &lt;J5Yr ^ nt'aT cqirrcmrfrr4 in a transparent conductive oxide (TCO) layer, which in turn is placed on the back surface of the semiconductor diode structure. Alternatively, the back surface metallization pattern for HIT cells may comprise a thin layer of copper placed on a TCO layer, which in turn is placed on a back surface of the semiconductor diode structure. The copper layer can be deposited by means of electroplating, for example. The TCO in this variation or the above may be of or comprise indium tin oxide, for example. Any other suitable back surface metallization pattern can also be used.

For HIT cells that are employed in solar cell strings as described in this document, a copper thin-film back surface metallization pattern can handle high current density with low resistance and thus results in loss. I²R goes down on rear contact. Light that passes unabsorbed through the HIT cell is generally absorbed by the copper layer, however this leads to optical loss. HIT cells in which the metallization pattern of₄₆ WICKED

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INDUSTRIAL posterior surface comprises fingers deposited in a TCO layer that can be positioned with their posterior surfaces on or above a reflective surface, such as a white surface. Light that passes unabsorbed through the HIT cell can be reflected in this way to the HIT cell, passing the fingers and through the TCO, to be absorbed into the HIT cell and generate additional current. Loss I²R on fingers may be higher than for copper thin-bed back surface metallization variation, however. The choice of the back surface metallization pattern generally depends on which pattern performs best when HIT cells are illuminated at a desired level of concentration (eg, greater than or equal to about seven suns).

Referring now to Figure 2, an exemplary solar energy receiver 45 comprises a string of serially connected solar cells 10 arranged in a superimposed manner on a linearly elongated substrate 50 .. Each solar cell 10 in the solar energy receiver 45 has the front and back surface metallization patterns illustrated in Figures 1A and IB, respectively. Figure 3A shows a cross-sectional view illustrating the overlap of adjacent solar cells in the solar power receiver 45. As shown in Figure

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3A, for each pair of superimposed solar cells the bottom contact pad 30 of one solar cell overlaps the front surface busbar 15 of the other solar cell. The front surface busbar 15 at one end of the chain and the exposed lower contact pad 30 at the other end of the chain can be used to electrically connect the chain to other electrical components as desired. In the example illustrated in Figure 2, the bypass conductors 40 are hidden by the overlapping portions of adjacent cells. Alternatively, solar cells comprising bypass conductors 40 can be overlaid in a similar manner as shown in Figure 2 and Figure 3A without covering the bypass conductors.

The front surface busbar 15 and bottom contact pad 30 of an overlapping pair of solar cells 10 can be joined together using any suitable electrically conductive bonding material. Suitable conductive bonding materials can include, for example, electrically conductive reflow soldering, and electrically conductive adhesives. Suitable electrically conductive adhesives may include, for example, interconnect pastes, conductive films, and conductive films. ⁴⁸

INSTITUTO MEXICANO anisotropic available from Hitachi ChemiccMiÑ ^ | Ku suppliers, as well as electrical tapes «» - ~ &amp; »« 4uctÍ.vas— .. available from Adhesives Research Inc., Glen Rock Pennsylvania, and other suppliers. Electrically conductive adhesives can also include silver conductive epoxies or other conductive epoxies. In some variations, such electrically conductive adhesives can be selected, for example, to remain flexible over a temperature range of between about -40 ° C and 115 ° C, have an electrical resistivity less than or equal to about 0.04 ohm centimeters, exhibit elongation at break greater than or equal to about 20%, have a removable viscosity, or have any combination of the above characteristics.

The illustration in Figure 3A labels the front busbars 15 with a minus sign (-), and the bottom contact pads 30 with a plus sign (+), to indicate electrical contact with the n-type and p-type conductivity layers at the solar cell, respectively. This labeling is not intended to be limiting. As noted above, solar cells can have any suitable diode structure.

<img file="MX347994B_D0022.tif" />

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Referring again to Figure 2, the substrate 50 of the solar energy receiver 45 can be, for example, an aluminum or other metal substrate, a glass substrate, or a substrate formed from any other suitable material. Solar cells 10 can be attached to substrate 50 in any suitable manner. For example, solar cells 10 can be laminated to an aluminum or other metal substrate 50 with interference adhesive, encapsulating layers, and / or electrically insulators positioned between solar cells 10 and the surface of the metal substrate. The substrate 50 may optionally comprise channels through which a liquid may be flowed to extract heat from the solar energy receiver 45 and thereby cool the solar cells 10, in which case the substrate 50 may preferably be a substrate of extruded metal. The solar energy receiver 45 can employ, for example, delamination structures, substrate configurations, and other receiver components or features as disclosed in US Patent Application No. Series 12 / 622,416, entitled Receiver for Concentrating Solar Photovoltaic-Thermal System, and presented on November 19, 2009, which is incorporated in this document by reference in its so IMPI »

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DtLAnOniTY O — J7 * tNnt'STWAL totality. Although in the illustrated example the substrate 50 is linearly elongated, any other suitable shape for the substrate 50 may also be used.

Receiver 45 may include only one row of solar cells running along its length, as shown in Figure 2. Alternatively, receiver 45 may include two or more parallel rows of solar cells running along its length. length.

Strings of superimposed series-connected solar cells as disclosed herein, and linearly elongated receivers including such strings, can be used, for example, in solar energy collectors that concentrate solar radiation in a linear focus along the length of the receiver, parallel to the string of solar cells. Concentrating solar energy collectors that may conveniently employ serially connected superimposed solar cell strings as disclosed herein may include, for example, solar energy collectors disclosed in United States Patent Application document. No. Series 12 / 781,706, entitled Concentrating Solar Energy Collector, and filed on May 17, 2010, and the solar energy collectors disclosed in the Patent Application document _Cil ΪΜΡΙ ^

1 United States rRsrnjrro Μβιο deο Serial No. 13 / 740,770, entitled Concentrating Solar Energy Collector, and filed on January 14, 2013. Each of these patent applications is incorporated into this document by reference in its entirety. Such concentrating solar energy collectors can employ, for example, long narrow flat mirrors arranged to approach a parabolic trough that concentrates solar radiation into a linear focus on the receiver.

Referring again to Figures IA and IB, although the illustrated examples show the front busbar 15 and the rear contact pad 30 each extending substantially the length of the long sides of the solar cell 10 with uniform widths, this it may be convenient but not required. For example, the front bus bar 15 can be replaced by two or more discrete contact pads that can be accommodated, for example, in line between them along one side of the solar cell 10. Such discrete contact pads can optionally interconnected by means of thinner conductors running between them. There may be a separate (e.g. small) touch pad for each finger in the front surface metallization pattern, or each touch pad can be connected to s2 IMPI

INSTTIVTO mUicanc n »THE INTENTAL NAME ___ two or more fingers. The rear contact pad 30 can be similarly replaced with two or more discrete contact pads. The front busbar 15 may be continuous as shown in Figure 1A, and the rear contact pad 30 formed of discrete contact pads has just been described. Alternatively, the front bus bar 15 can be formed from discrete contact pads, and the rear contact pad 30 formed as shown in Figure IB. As yet another alternative, both the front bus bar 15 and the rear contact pad 30 can be replaced by two or more discrete contact pads. In these variations, current pickup functions that would otherwise be carried out by front bus bar 15, rear contact pad 30, or by front bus bar 15 and rear contact pad 30 can be instead carried out, or partially carried out, by the conductive material that is used to bond two solar cells 10 to one another in the overlapping configuration described above.

Although Figure IB and Figure 3A show the rear contact pad 30 located adjacent a long edge of the rear surface of the solar cell 10,

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CE LARORIEDAL Contact pad 30 can have any suitable ^ u ^ icacTOT on the rear surface of the solar cell? 'For example, Figures 6A-6C, 7B, and 8B, described further below, show solar cells 10 examples each having a contact pad 30 located near the center of the rear surface of the solar cell and running parallel to the long axis of the solar cell.

Furthermore, solar cell 10 may lack front busbar 15 and include only fingers 20 in the front surface metallization pattern, or lack contact pad 30 and include only contact 25 in the rear surface metallization pattern. , or lack the front busbar 15 and lack the rear contact pad 30. In these variations as well, current pickup functions that would otherwise be carried out by means of the front busbar 15, the rear contact pad 30, or the front busbar 15 and the rear contact pad 30 can be rather carried out by the conductive material that is used to bond all solar cells 10 to one another in the overlapping configuration described above.

<img file="MX347994B_D0024.tif" />

Solar cells that lack busbar 15, or have busbar 15 replaced by discrete contact pads, may include bypass conductor 40, or not include bypass conductor 40. If the bus bar 15 is absent, the bypass conductor 40 can be accommodated to bypass the cracks that form between the bypass conductor and the portion of the front surface metallization pattern that is conductively bonded to the superimposed solar cell.

Up to this point, solar cells 10 have been described as having front and back surface metallization patterns that provide electrical contact to opposite sides of a diode junction. Alternatively, the solar cells 10 may be back-contact solar cells in which one set of contacts on the back surface of the solar cell electrically contacts one side of the diode junction, and another set of contacts on the back surface of the solar cell. the solar cell makes electrical contact with the other side of the diode junction. When such solar cells are deployed in a conventional manner, generally no electrical contact is made at the front surface of the solar cells. This back contact geometry conveniently increases the amount of incident light on the active portions of the solar cell.⁵⁵

MEXICAN INSTITUTE _Ί „_Ί ___ _Ί 4 .-, · -, removing the surface metallization 'íT'OT' &amp; al ^ '- qttC would block the light. Such -eotrbacLo solar cells¹ pus¹ Le110T are available, for example, from SunPower Inc.

When used in strings in a solar cell shingle fashion as described herein, such a rear contact solar cell may further include conduction pathways that pass through the solar cell from its rear surface to its front surface to provide , at an edge of the front surface, one or more electrical connections to one side of the diode junction. When the solar cell is accommodated in a shingle fashion with a similarly configured solar cell adjacent, the front surface electrical connections on the edge of one cell overlap with and may be electrically connected to back surface contacts on the other cell. to electrically connect the two superimposed back contact solar cells in series.

Figures 1C-1E schematically depict an exemplary full back contact solar cell 10 configured for use in a string of superimposed solar cells (ie, in a shingle fashion) connected in series. The exemplary posterior surface metallization pattern shown in Figure 1C and Figure 1E includes an optional p-line that runs parallel to and adjacent to the long side of

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OF THE FBORSITY of the solar cell, a plurality of fingers p 24 connect line p and running parallel to the short sides of the solar cell, an optional line 26 running parallel and adjacent to the other long side of the solar cell, and a plurality of n fingers 28 connected to line n, running parallel to the short sides of the solar cell, and interdigitated with fingers p 24. The regions of the semiconductor structure below and in contact with the n-fingers are correspondingly doped with non-p-type to form a diode junction.

As seen in Figures 1C-1E, the exemplary back contact solar cell 10 also includes connection pathways 32 that pass through the solar cell 10 to provide electrical contact from line # 26 and fingers # 28 at the surface. rear of the solar cell 10 to an optional bus bar 24 that runs parallel and adjacent to a long side of the solar cell on the front surface of the solar cell. Figure ID represents the front surface of the solar cell 10 as if that front surface were seen through the rear surface of the solar cells. As shown by a comparison of Figures 1C-1E, in the illustrated exemplary bus 32 and line n 26 are positioned along the same long side of the solar cell, with line p

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positioned along the opposite long side. Solar cells configured in this way can be positioned with the p line 22 on the rear surface of a superimposed solar cell and electrically connected to the bus bar on the front surface of an adjacent solar cell to connect the solar cells in series. In this arrangement, the busbar 34 is covered by an active portion of the superimposed solar cell. Therefore, there is no exposed front surface metallization blocking light from the active regions of the solar cell.

Alternatively, the polarities n and p in the above description can be interchanged such that vias 32 provide electrical contact from contacts p on the rear surface of solar cell 10 to bus bar 34 on the front surface. Solar cells configured in this way can be positioned with line n on the back surface of a superimposed solar cell and electrically connected to the bus bar on the front surface of an adjacent solar cell to connect the two solar cells in series.

Although the illustrated examples show one pathway for each finger on the rear surface to be electrically connected to the front surface, there may be more or fewer pathways than fingers as long as the fingers per _5β IMPI ^ ° ΙΙΤΓΤΤΤντΟ MIllCANc '&amp; SeC of the nortiMD ÍNDUSTSUl connect to the front surface are interconnected on the rear surface in such a way that each is electrically connected to one or more pathways.

Although the bus bar 34 is shown as extending substantially the entire length of the long sides of the solar cell 10 with uniform width, this may be convenient but not required. For example, bus bar 34 can be replaced by two or more discrete contact pads which can be accommodated, for example, in line with each other along one side of solar cell 10. Such discrete contact pads can optionally be interconnected by means of thin conductors running between them. There may be a separate (eg, small) touch pad on the front surface for each track, or each touch pad can be connected to two or more tracks. Busbar 34 may also be absent. Line p 22 and / or line n 26 can be similarly replaced by two or more discrete contact pads, or they can be absent.

Some variations lack a busbar 34 at the front surface end of the tracks, or lack an interconnecting conductor such as a line p or a line n at the rear surface end of the tracks, or lack a busbar 34 at the surface end

<img file="MX347994B_D0026.tif" />

IMPI

INSTITUTO MEJICANO DílARBOUSDAC upper tracks and also lack an interconnecting conctuc at the end of rear surface '' ele * la^rs' ways. In variations in which busbar 34, p-line 22, and / or n-line 26 are formed from discrete contact pads or are absent, current pickup functions that would otherwise be performed by By means of these characteristics, they may rather be carried out, or partially carried out, by means of conductive material that used to join together two solar cells in the overlapping configuration described above.

To shorten the current path between the overlapping back contact solar cells through the pathways described above, it may be desirable to configure and / or accommodate the solar cells such that each path is aligned at one end with the end of a finger. (nop) on the back surface of a solar cell and aligned at its other end with the end of a finger (pon) of opposite polarity on the back surface of an adjacent superimposed solar cell. With the fingers configured as shown in Figure 1C, the vias can be aligned in this manner by positioning the overlapping solar cells such that one translates relative to the other along their long overlapping sides by

- LMPI ^

ΓΝΤΓΠνΤΟ MEXICAN QF THE PROPERTY J a distance equal to the step between the¹” ^AIToesT Alternatively, the fingers may be configured as shown in Figure 1F, for example, such that they extend at an angle across the rear surface of the solar cell such that the opposite ends of each finger are out of phase. along the long sides of the solar cell for a distance equal to the pitch between the fingers. Solar cells configured in this manner can be overlapped with their short sides flush to provide the desired track alignment with the fingers in the overlapping solar cells. Although Figure 1F shows the posterior surface metallization pattern that includes line p 22 and line n 26, either or both may be absent.

Tracks 32 can therefore interconnect two superimposed back contact solar cells finger to finger, finger to line (eg, busbar, p-line, or η-line), or line-to-line, for example.

The formation of pathways 32 can be integrated into conventional manufacturing processes for full back contact solar cells. The holes for the vias can be formed, for example, by means of conventional laser drilling and can be filled, for example, with any suitable conventional conductive material deposited by means of any suitable conventional method. The conductive material can be an electroplated metal or a printed conductive metal paste, for example.

Back-contact solar cells can also be employed in series-connected superimposed solar cell strings without using the pathways described above. Referring to the cross-sectional view of Figure 3B, for example, two such superimposed back contact solar cells may be electrically connected in series by means of a mechanically shaped electrical interconnect 90 that interconnects a back contact in one of the solar cells. and a back contact of opposite polarity on the other solar cell.

The series-connected superimposed solar cell strings disclosed herein, and the linearly elongated receivers that include such strings, must operate more efficiently than conventional arrangements, particularly under concentrated lighting. In some variations, the overlapping solar cell strings disclosed herein can provide, for example, or 15% more energy output than conventionally analogous accommodated solar cell strings.

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OR ΙΝΤΠΚΓΓΟ MEXICAN

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INDUSTRY!

Dice-cutting a wafer to provide solar cells that have smaller areas reduces the current I generated in the solar cells and can in this way reduce the energy losses I ^ R that result from the resistance R internal to the solar cells and the resistance in connections between solar cells in a chain. However, conventional strings of solar cells connected in series require spaces between adjacent solar cells. For a string of a given physical length, the number of such spaces increases as the solar cells get shorter. Each space reduces the energy generated by the chain, thereby at least partially overcoming the advantage that could otherwise result from using solar cells from smaller areas. Furthermore, the resulting energy loss from the gaps increases when such a conventional string is employed in a concentrating solar energy collector.

In contrast to conventional solar cell strings, the series connected superimposed solar cell strings disclosed herein do not have gaps between solar cells. Solar cells in such strings can in this way be diced into smaller areas to reduce I'R losses without accumulating energy losses due to gaps. For example, you can

<img file="MX347994B_D0027.tif" />

IMPI iNsTrruro in Mexico, it is advisable to use solar cells that have a longer side that has a length that covers a standard wafer, as in the solar cells 10 that are represented in the different figures in this document, because such solar cells can be oriented with its longer sides perpendicular to the long axis of the string to provide a wider focal region in a linear focus concentration solar energy collector. (Making the focal region wider relaxes the tolerances on the optical elements in the concentrating solar energy collector, and can facilitate the convenient use of flat mirrors.) For conventional solar cell strings, the optimal length of the short side of the solar cells would then be determined, in part, by a trade-off between the energy losses I²R and losses due to gaps between cells. For the overlapping solar cell strings disclosed in this document, the length of the short sides of the solar cells (and therefore the areas of the solar cells) can be selected to reduce IR losses to a desired level without concern. for losses due to spaces.

Conventional solar cells generally employ two or more parallel front surface bus bars

ΙΝΕΤΤτνΤΟ M £ XIGAN (

Dt LA HOFIEDAf AsmÍEIJ INDUSTRIAL which darken the underlying portions of the solar cells and thereby reduce the energy generated by each solar cell. This problem is exacerbated by copper slats, generally wider than bus bars, which are used in conventional strings to electrically connect the front surface bus bars of a solar cell to the rear surface contact of an adjacent solar cell in the string. . The copper slats in such conventional strings generally run across the front surface of the solar cells, parallel to the string and overlying the bus bars. The energy losses resulting from dimming by the bus bars and by the copper slats are increased when such conventional solar cells are used in a concentrating solar energy collector. In contrast, the solar cells disclosed in this document may employ only a busbar on their front surfaces, as illustrated, or no busbar, and do not require copper slats running across the illuminated front surface of the solar cells. . Furthermore, in overlapping solar cell strings as disclosed herein, the front surface busbar on each solar cell, if present, can be hidden by the active surface area of ​​an overlapping solar cell, except at one end.

IMPI '»« πτηποΜαιο * Νο from the string. The solar cells and solar cell strings disclosed in this document can therefore reduce_Ksignificantly losses due to darkening of the underlying portions of the solar cells by front surface metallization, compared to conventional configurations.

A component of energy losses I²R is due to the current paths through the fingers in the front surface metallization. In conventionally accommodated solar cell strings, the bus bars on the front surfaces of the solar cells are oriented parallel to the length of the string, and the fingers are oriented perpendicular to the length of the string. The current within a solar cell in such a conventional string flows mainly perpendicular to the length of the string along the fingers to reach the bus bars. The finger lengths required in such geometries can be long enough to result in significant IR energy losses at the fingers. In contrast, the fingers in the front surface metallization of solar cells disclosed in this document are oriented parallel to the short sides of the solar cells and parallel to the length of the string, and the current in a solar cell mainly flows parallel

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6 INSTITUTO MEXICANO de la frofieda: 0ν ^ ™ 3Εί1ΛΑ · /. INDUSTRIAL to the length of the chain along the fingers. The * · “· '&lt;111 II» «A ··· .- HIL'I I — l finger lengths required in this arrangement can be shorter than those required for conventional cells, thus reducing energy losses.

Other component of energy losses I²R is due to the length of the current path between adjacent solar cells through conventional copper batten interconnects. The current paths between adjacent solar cells in the overlapping configurations disclosed herein may be shorter than in conventional arrangements, thereby reducing I losses.²R.

The solar cell metallization patterns and / or overlapping cell geometries disclosed herein can be conveniently used with crystalline silicon solar cells placed on a metal substrate, as in the receiver 45 of Figure 2, for example. However, someone experienced in the field may find this surprising. If formed using conventional reflow soldering, for example, the junction between the front surface busbar and the back surface contact pad of superimposed solar cells in a chain as disclosed herein can be significantly stiffer than the connections.

<img file="MX347994B_D0028.tif" />

IMPI

INSTITUTO MUICaM * r »LA MOHtnAtl

INOlfS-rttAI electrics between solar cells are provided by means of adjacent tabs that are copper strip on conventional solar cell string of tabs. Consequently, compared to the use of copper batten tabs, solder connections between adjacent solar cells in such a string can provide significantly less strain relief to accommodate the mismatch between the coefficient of thermal expansion (GTE,

Coefficient of Thermal Expansion) of silicon solar cells and that of the metal substrate. That mismatch can be quite large. For example, crystalline silicon has a GTE of ~ 3 * 10-⁶, and aluminum has a GTE of ~ 23 χ 10-⁶. One of ordinary skill in the art can therefore expect that such superposed strings of silicon solar cells placed on a metal substrate will fail due to cracking of the silicon solar cells. This expectation would be even stronger and for such superimposed solar cell strings used in a concentrating solar energy collector in which they could cycle through larger temperature ranges, and therefore experience greater deformation due to expansion mismatch thermal with the substrate, than what is generally experienced in a non-concentrating solar energy collector.

iMPie _lNrrrrvro mexican Ȣ ,.

Contrary to such expectations, however, the inventors have determined that strings of superimposed silicon solar cells connected in series can be joined together with conventional reflow soldering, joined to an aluminum or other metal substrate, and operated in reliably under concentrated solar radiation. Such chains may have a length, for example, greater than or equal to about 120mm, greater than or equal to about 200mm, greater than or equal to about 300mm, greater than or equal to about 400mm, greater than or equal to about 500mm, or between approximately 120mm and 500mm.

Furthermore, the inventors have also determined that solder substitutes such as those described above, including electrically conductive tapes, conductive films, interconnect pastes, conductive epoxies (eg, silver conductive epoxies), and others similar conductive adhesives, for example They can be used to bond solar cells together to form even longer chains of superimposed solar cells connected in series on a metal substrate. In such variations, the conductive bonding material that binds the overlapping cells together is selected to be shaped "IMPI ^

INSTITUTO MEXICANO tu LA PROWFDAF. . : '' and mechanically, by which it is understood that the union 'Y ^ T ^' rial 'is elastically deformed easily - ϋδΛιοTesorte. (Mechanical compliance is the inverse of stiffness). In particular, the conductive joints between solar cells in such chains are selected to be more mechanically shaped than solar cells 10, and more mechanically shaped than conventional reflow solder connections that could otherwise be used between the superimposed solar cells. . Such mechanically formed conductive bonds between the superimposed solar cells deform without cracking, dislodging from adjacent solar cells, or otherwise failing under deformation that results from thermal expansion mismatch between solar cells 10 and substrate 50. The mechanically formed junctions can therefore provide stress relief to a chain of interconnected, overlapping solar cells, thereby accommodating the CTE mismatch between solar cells 10 and substrate 50 and preventing the chain from failing. The difference between the CTE of the solar cell (e.g. silicon) and the substrate can be, for example, greater than or equal to about 5 * 10⁶, greater than or equal to about 10 * 10 '⁶, greater than or equal to approximately 15 χ 10 "⁶, or greater than or equal to about 20 x 10 \ Such silicon solar cell strings

<img file="MX347994B_D0029.tif" />

IMPI

INSTITUTO MEXICANO DE LA RSDfIBDAD INDUSTRIAL superimposed series connected placed on a substrate with

Misadjusted CTEs can have a length, for example, greater than or equal to about 1 meter, greater than or equal to about 2 meters, or greater than or equal to about 3 meters.

Furthermore, the inventors have developed mechanically formed electrical interconnects that can be used to interconnect two or more strings of superimposed solar cells interconnected in series to form longer strings of solar cells connected in series. The resulting longer chains can be laid on a metal or other substrate and operate reliably under concentrated solar radiation. Referring now to Figure 4, an exemplary string 55 of serially connected solar cells comprises a first group 60 of serially connected superimposed solar cells 10 that are electrically and physically connected to a second group 65 of serially connected superimposed solar cells 10 by means of a mechanically shaped electrically conductive interconnect 70. Additional interconnects 70 are located at the ends of string 55 to allow additional groups of superimposed solar cells connected in series to be added to either end of string 55 to extend the length of the string. Alternatively, the interconnections

<img file="MX347994B_D0030.tif" />

IMPI nmrruro mkicamo OBUnOHBlMD INDUSTRIAL that are located at the ends of a chain can be used to interconnect the chain to other electrical components or an external load. The overlapping solar cells within groups 60 and 55 can be joined together with electrically conductive reflow soldering or electrically conductive adhesives, as described above, or in any other suitable manner.

The spacing between the adjacent ends of two groups of superimposed solar cells 10 connected in series interconnected with a mechanically formed interconnect 70 may be, for example, less than or equal to about 0.2 mm, less than or equal to about 0.5 mm, less than or equal to about 1mm, less than or equal to about 2mm, less than or equal to about 3mm, less than or equal to about 4mm, or less than or equal to about 5mm.

The variation of the mechanically formed electrical interconnect shown in Figure 4 is also shown, in greater detail, in Figure 5A. Another variation of the mechanically formed electrical interconnect 70 having similar characteristics is shown in Figure 5B. Referring now to Figure 5A and Figure 5B as well as Figure 4, the electrical interconnections 70

IMPI® ^{7 2} iNOtmiAi -------- mechanically shaped are strip type and have a long, narrow aspect ratio with a length approximately equal to or greater than the length of the long sides of the solar cells 10. Each interconnect 70 * comprises two assemblies of tabs positioned on an opposite side of the long axis of the interconnect. As shown in Figure 4, an interconnect 70 may be positioned between two strings of superimposed solar cells connected in series with their tabs 75 on one side making electrical contact with the bus bar 15 on the front surface of an end solar cell of a chain of superimposed solar cells, and with its tabs 75 on the other side making electrical contact with the rental contact pad on the rear surface of one end cell of the other superimposed solar cell string. Tabs 75 may be attached to bus bar 15 or contact pad 30 with conventional electrically conductive solder, electrically conductive adhesives as described above, or by any other suitable method.

In the example of Figure 4, the interconnects 70 at the end of string 55 also each include a bypass diode socket 80 at one end, in addition to the tabs.

75. Bypass diode taps 80 provide points

IMPI rirmUTO muucano nor LA * ROmOAD INDUSTRIA!

connection for bypass diodes. In the illustrated example, bypass diode 85 is configured to bypass both groups of superimposed solar cells connected in series in the event that one solar cell in string 55 fails. Alternatively, interconnects 70 having bypass diode taps 80 may be used at any desired range in a string to bypass one, two, or more groups of superimposed solar cells connected in series. The maximum number of solar cells that can be accommodated to bypass by means of a bypass diode is determined by the performance characteristics of the bypass diode. The bypass diodes to be configured to bypass, for example, about 25 solar cells 10, which may be distributed into any desired number of series connected groups of superimposed series connected solar cells. For example, each bypass diode can be configured to bypass approximately 25 solar cells, all of which are part of a single group of superimposed solar cells connected in series. Although in the illustrated example the bypass diode is connected to the chain with interconnects 70, alternative configurations can also be used. For example, bypass diodes can be connected to the chain by means of a

<img file="MX347994B_D0031.tif" />

4

IMPI

IIWTlTUro MEXICANO DE LA MOHEDAL INDUSTRIAL conductor (other than an interconnection 70) that is electrically connected to the lower metallization pattern of a solar cell, and by another conductor (a different one, an interconnection 70) that is electrically connected to a bus bar in the front surface of another solar cell. Such connections can be made to solar cells that are not at the end of a group of superimposed solar cells connected in series, but rather somewhere in between.

Referring now to Figure 11, bypass diode 85 may be mounted in a flexible circuit 87 comprising two physically separate electrical contacts 92 sandwiched between two insulation sheets. The insulation sheets are patterned to expose adjacent regions 93 of the two contacts to which the diode is attached to electrically interconnect the contacts, and to expose the regions 97 of the contacts allowing the flex circuit to be electrically connected to bypass a portion of the solar cell chain. Each of the contacts 92 is shaped or patterned to enhance their mechanical compliance. In particular, the contacts 92 include narrow necks and oval-shaped regions that make the contacts highly shaped. Contacts 92 can be formed, for example, from metal strip (eg, copper) coated with

IMPI iwrmno μεϊιομπ DI LA HieHEDAt: INDUSTRIAL welding. Insulation sheets can be formed, for example, from a polyimide. Flexible circuit 87 may further comprise a lower adhesive layer by means of which it can be attached to a substrate supporting a string of solar cells.

Referring again to Figure 4, Figure 5A, and Figure 5B, the interconnects 70 are mechanically formed. In particular, they are more mechanically shaped than the solar cells 10 and more mechanically shaped than the solder connections between the bus bar 15 and the back contact pad 30 of the superimposed solar cells 10. The interconnects 70 may also be more mechanically shaped than the joints between the overlapping solar cells formed from electrically conductive adhesives as described above. Interconnects 70 deform without cracking, detaching from adjacent solar cells, or otherwise failing under deformation resulting from thermal expansion mismatch between solar cells 10 and substrate 50. The interconnections 70 can therefore provide stress relief to a chain of interconnected groups of overlapping solar cells, thereby accommodating the thermal expansion mismatch between the solar cells 10 and the substrate 50 and preventing the chain from failing.

In the illustrated examples, each interconnect 70 is a solder-coated metal (eg, copper) slat that is shaped or patterned to enhance mechanical compliance. In particular, the interface 70 illustrated in Figure 5A includes a central portion that is in the form of a series of two or more flattened ovals intertwined at their ends. Each flattened oval includes a pair of tabs 75 on opposite flattened sides of the oval, for contacting the solar cells as described above. The flattened ovals make each interconnect 70 highly conformed (like springs) in directions parallel and perpendicular to the long axis of the interconnect. In the example illustrated, the metal strips that form the walls of the ovals have a width W1 of approximately 1.5mm, but any suitable width can be used. The illustrated interface 70 of Figure 5B includes a series of grooves running through the center of the metal slat parallel to its long axis. The grooves make the interconnection of this variation very shaped, too. Interconnects 70 can be formed from highly conductive materials such as copper, for example, and / or from materials such as Invar (a nickel-iron alloy) and Kovar (a nickel-cobalt alloy „IMPI ^ '' mexican institute

D «LA PMXWMD industrial iron) which have a low coefficient of thermal expansion. Each metal slat may be sandwiched between thin insulation sheets of material to form a flexible circuit, with the patterned insulation sheets to expose portions of the metal slat (e.g., tabs 75) that are intended to make electrical contact. with solar cells. Insulation sheets can be formed from a polyimide, for example.

Any other suitable material and configuration may also be used for the interconnects 70 which interconnect two series connected strings of superimposed solar cells. For example, the interconnects 70 may be similar or identical to any of the mechanically formed interconnects 90 described below with respect to Figures 6A-6C, 7A, 7B, 8A, 8B, or 9. Also, two or more interconnects 70 can be arranged in parallel in a similar manner as shown in Figures 7A and 7B described below to interconnect two groups of superimposed solar cells connected in series.

Although the use of interconnects 70 was previously described with respect to solar cells 10 that include front surface bus bars 15 and rear contact pads 30, such interconnects 70 can be used in combination with any of the variations of

<img file="MX347994B_D0032.tif" />

IMPI * iiwhtvto Mexicano f »F LA PHOFltDAD INDWTRIAI the solar cell described in this document. In variations lacking the busbars 15, the back contact pads 30, or both, the interconnects 70 can be attached to the solar cells 10 using electrically conductive adhesives as described above, for example.

Mechanically shaped electrical interconnects similar or identical to interconnects 70 can also be used between each solar cell in a string of solar cells connected in series, or between each solar cell in a contiguous portion of three or more solar cells of the string connected in series. series of solar cells. As shown in Figures 6A-6C, 7A, 7B, 8A, 8B, and 9, for example, each pair of superimposed solar cells 10 in a series connected string of superimposed solar cells can be physically and electrically connected by means of the mechanically formed interconnects 90, each of which interconnects the front surface metallization of a solar cell with the rear surface metallization of an adjacent solar cell. Such strings differ from conventional reed strings at least because the adjacent solar cells in the illustrated strings overlap, and because the locations at which the interconnects 90 are attached to the front surfaces of

IMPI ^

MEXICAN INSTITUTE

OF ΙΑ ΜΧΙΗΕΟΑΓ INDUSTRIAL — solar cells 10 may be hidden from lighting by an overlapping solar cell. The mechanically formed interconnects 90 can be attached to the solar cells 10 with, for example, conventional electrically conductive welding, electrically conductive adhesives, adhesive films, or adhesive tapes as described above, or by any other suitable method.

Interconnects 90 are mechanically formed.

In particular, they are more mechanically shaped than the solar cells 10 and more mechanically shaped than the solder connections between the bus bar 15 and the back contact pad 30 of the superimposed solar cells 10. The interconnects 90 may also be more mechanically shaped than the overlapping solar cell junctions formed from electrically conductive adhesives as described above. Interconnects 90 deform without cracking, detaching from adjacent solar cells, or otherwise failing under deformation resulting from thermal expansion mismatch between solar cells 10 and a substrate to which they are attached. Interconnections 90 can therefore provide stress relief to a chain of interconnected groups of overlapping solar cells, thereby accommodating the thermal expansion mismatch between the so IMPI ^ iNirrvuiu mexicana

DI LA HOHEDAD i INDUSTRIAL solar cells 10 and a substrate and preventing the chain from failing.

Interconnects 90 can be formed, for example, from highly conductive materials such as copper, one example, and / or from materials such as Invar and Kovar that have a low coefficient of thermal expansion. Interconnects 90 may be of or comprise solder coated copper slats, for example. Alternatively, the interconnects 90 may be or comprise copper slats sandwiched between layers of polyimide (eg, Kapton films) or other layers of insulation, with the layers interspersed in a pattern to expose the copper slat at the locations to be they are going to join the solar cells. Any other materials and configurations can be used for interconnects 90 in addition to those disclosed in this document.

Figures 6A-6C show exemplary cross-sectional views illustrating the interconnection of a string of superimposed solar cells 10 with mechanically formed electrical interconnects 90. One illustrated in these examples, the interconnects 90 may have a flat cross-sectional profile (Figure 6A), a bent cross-sectional profile (Figure 6B), or a curved cross-sectional profile (Figure 6C). Any other suitable cross-sectional profile can also be used. Bent or curved cross section profiles can increase mechanical compliance, compared to a flat cross section profile.

In the examples illustrated in Figures 6A-6C and later figures, the rear contact pad 30 is located away from the edge of the solar cell 10, near the middle of the rear surface. This is not required. The contact pad 30 can be positioned at any suitable location on the rear surface of the solar cell. For example, contact pad 30 may be positioned adjacent to the overlapping edge of solar cell 10, as shown in Figure IB, or adjacent to the opposite edge of the overlapping edge.

Figures 7A and 7B show front and rear views, respectively, of an exemplary string of superimposed solar cells connected in series. As shown in these figures, two or more interconnects 90 may be arranged in parallel with each other to interconnect adjacent superimposed solar cells. In the illustrated example, the interconnects 90 are in the form of slats with their long axes oriented perpendicular to the overlapping edges of adjacent solar cells. As another example (not shown), the parallel interconnects 90 may have the same

<img file="MX347994B_D0033.tif" />

form of two or more slats arranged in

IMPI rwnwro MExiCANi

DE LA rtC * 1U&gt; AD industriai line between them with their long axes oriented parallel to the overlapping edges of adjacent solar cells.

Figures 8A and 8B show front and rear views, respectively, of another exemplary string of superimposed solar cells connected in series. Figure 9 shows a rear view of yet another exemplary string of superimposed solar cells connected in series. As shown in Figures 8A, 8B, and 9, the interconnects 90 may be in the form of slats oriented parallel to and extending along the length of the overlapping edges of adjacent solar cells.

The 90 exemplary interconnections illustrated in the

Figures 8A and 8B are similar or identical to the interconnects 70 illustrated in Figure 4 and Figure 5. In the variation illustrated in Figures 8A and 8B, each interconnect 90 includes two sets of tabs 75, with each set barb positioned on an opposite side of the long axis of the interconnect. Such interconnection 90 may be positioned between two superimposed solar cells with their tabs 75 on one side making electrical contact with the bus bar 15 on the front surface of one of the solar cells, and with their tabs 75 on the other side making electrical contact with touch pad 30

<img file="MX347994B_D0034.tif" />

on the posterior surface of the

IMPI

INSTITUI # MEXICANO Di LA noniDAD another cell sol'S'ST '^ an ^ i as illustrated in Figures 8A and 8B, the IhL'óTconnections' ”may optionally include bypass diode sockets 80 that provide connection points for the Bypass configured to bypass one or more solar cells in the event that one of the solar cells fails.

The exemplary interconnects 90 illustrated in Figure 9 are in the form of patterned rectangular slats with slits or openings 95 that enhance their mechanical compliance. The illustrated interconnects 90 also include contact pads 100 to be attached to the solar cells. Such interconnects 90 can be, for example, or comprise copper slats sandwiched between layers of polyimide (eg, Kapton films) or other layers of insulation, with the layers interspersed in a pattern to expose the copper slat at the locations contact pads 100.

Although the use of interconnects 90 was previously described with respect to solar cells 10 that include front surface busbars 15 and rear contact pads 30, such interconnects 90 can be used in combination with any of the variations of solar cell 10 described in this document. In variations that₈₄ IMPI ^ n'STTJVFO MEXICAN

Of the NOWIDAL fNDUSTRlAl lacking bus bars 15, back contact pads 30, or both, the interconnects 90 can be attached to the solar cells 10 using electrically conductive adhesives as described above, for example.

Referring now to Figure 10, a string of solar cells 10 can be placed on a substrate 50 in a lamination stack 105 that is adhered to the substrate. The lamination row may comprise, for example, a thermally conductive encapsulating layer 110 positioned between the solar cells and the substrate, a transparent encapsulating layer 115 positioned on the thermally conductive encapsulating layer, and a transparent topsheet 120 positioned on the transparent encapsulating layer. 115. Solar cells 10 are generally positioned within transparent encapsulating layer 115 at their border with thermally conductive encapsulating layer 110.

Thermally conductive encapsulating layer 110 comprises one or more materials that are selected to facilitate heat transfer from solar cells 10 to substrate 50 and / or to adhere substrate 50, solar cells 10, and transparent encapsulating layer 115. The material in the encapsulating layer 110 can be selected to adhere to aluminum or aluminum-based alloys, for example. The thermally conductive encapsulating layer 110 may have a thickness, for example, of about 0.1 .________{Ί [}___r_ , ,------ ¹ MI '·· * millimeters to 2.0 millimeters.

In the illustrated example, the thermally conductive encapsulating layer 110 comprises a first layer of thermally conductive adhesive 125, a dielectric layer 130, and a second layer of thermally conductive adhesive 135. The dielectric layer 130 generally melts at a higher temperature than the surrounding adhesive layers, and consequently provides a barrier to physical and electrical contact between the solar cells 10 and the substrate 50 that survives a lamination process, described below, by means of which the lamination stack 105 is attached to the substrate 50. The adhesive layer 125 can comprise, for example, one or more thermally conductive polyolefins and can have a thickness, for example, from about 0.1 millimeters to 2.0 millimeters. Dielectric layer 130 can comprise, for example, one or more fluoropolymers. Fluoropolymers can be selected, for example, from the group including, but not limited to, polyvinyl fluoride (PVF, Polyvinyl Fluoride), polyvinylidene fluoride (PVDF, Polyvinylidene Fluoride), ethylene tetrafluoroethylene, and mixtures thereof. Dielectric layer 130 may have a thickness, for example, from about 0.1 millimeters to 2.0 millimeters. The adhesive layer 135 may comprise, for₈₆ IMPI ^

OE LA EROmtAC '^ at-r ^ íú INDUSTRIAL “example, one or more thermally conductive polyolefins and may have a thickness, for example, from about 0.1 millimeters to 2.0 millimeters.

Any other suitable material and configuration may be used for the thermally conductive encapsulating layer 110 and its component layers 125, 130, and 135 described above. For example, in some variations the dielectric layer 130 is absent. In such variations, the encapsulating layer 115 can be, for example, a single layer of thermally conductive polyolefin.

The uniquely conductive encapsulating layer 110 may be substantially reflective to solar radiation incident thereon. For example, the materials in the encapsulating layer 110 may include pigments that make the encapsulating layer 110 appear white. Such a reflective encapsulating layer 110 reduces the heat absorbed by the lamination stack 105, which can conveniently improve the efficiency with which the solar cells 10 operate. Furthermore, if the solar cells 10 are HIT solar cells with finger-comprising back surface metallization, as described above, then such a reflective encapsulating layer can reflect the light that has passed unabsorbed through the HIT solar cell back. to the solar cell where it can be absorbed to generate current

IMPI ^

7 IMSTHVrOMBlCAMC nt the miriBD ai:

INWSTRJAl 'additional ruLíJ, increasing the efficiency with which solar cells operate. Alternatively, the thermally conductive encapsulating layer 110 may be substantially absorbing the solar radiation incident thereon. For example, the materials in the encapsulating layer 110 can include pigments that make the encapsulating layer 110 appear black. Such an absorbent encapsulating layer 110 can increase the heat absorbed by the lamination stack 105 and subsequently transferred to the substrate 50, which may be desirable if the captured heat is commercially valuable.

Referring again to Figure 10, the transparent encapsulating layer 115 can comprise, for example, a transparent polyolefin, a transparent polyimide, a mixture thereof, and can have a thickness of, for example, about 0.1 millimeters to 2.0 millimeters. Any other suitable material and thickness can be used for the transparent encapsulating layer 115.

The transparent topsheet 120 may comprise, for example, one or more transparent fluoropolymers. Fluoropolymers can be selected, for example, from the group that includes, but is not limited to, polyvinyl fluoride (PVF), ethylene tetrafluoroethylene, and mixtures thereof. Clear topsheet 120 can be selected to

<img file="MX347994B_D0035.tif" />

IMPI

INSTITUTE MWCANC

M THE PROPERTY

INOUSTRIAt that has a moisture transmission rate less than or equal to approximately 0.01 grams / meter-day, for example. The transparent topsheet 120 may have a thickness, for example, from about 0.1 millimeters to 1.0 millimeters. Any other suitable material and thickness can be used for the clear topsheet 120.

Solar cells 10 in lamination stack 105 may be or comprise any of the solar cells disclosed herein, and may be accommodated in any of the serially connected, superimposed solar cell string configurations disclosed herein. . Any other suitable solar cell and string configuration can also be placed in the laminating stack 105, however. For example, although the solar cells 10 in Figure 10 are shown as overlapping in a shingle pattern, the solar cells placed in the stack 105 may be configured rather in a non-overlapping and conventional tab fashion.

The layers of components from lamination stack 105 can be positioned on a substrate 50 and then attached to substrate 50 in a conventional laminator, for example, at elevated temperature and with the application of directed pressure to force lamination stack 105 and the substrate 50 so that they come together. During this lamination process, the

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The temperature of the substrate 50 and / or the lamination stack 105 can be raised, for example, to between about 130 ° C and 160 ° C. If the solar cells in the lamination stack 105 are configured in a non-overlapping manner, the pressure applied during the lamination process can be about 1.0 atmosphere, for example. The inventors have determined, however, that if the solar cells in the lamination stack 105 are configured in an overlapping manner, as described herein, for example, the maximum pressure applied during the lamination process may preferably be less. or equal to approximately 0.6 atmospheres, less than or equal to approximately 0.5 atmospheres, less than or equal to approximately 0.4 atmospheres, less than or equal to approximately 0.3 atmospheres, or between approximately 0.2 atmospheres and 0.6 atmospheres.

In variations in which the overlapping solar cells are bonded together with a conductive epoxy such as a conductive epoxy with silver, for example, it may be preferable to cure the epoxy while applying pressure to force the solar cells against each other. Curing the conductive junction under pressure in this way can reduce the thickness of the conductive junction, thereby reducing the current path between the solar cells and in₉₀ IMPI »

THE PROWEDAt; '% 2_®Ϊ0 INDUSTRIAL consequence reducing losses I²R in the string cTe ”solar cells. In one approach, the conductive joints are cured under pressure to provide a series connected string of superimposed solar cells before the string is laminated to a substrate. In this approach, conduction joints can be cured at a temperature of, for example, about 150 ° C to 180 ° C and under a pressure of, for example, about 0.1 atmospheres to 1.0 atmospheres, or about 0.1 to 0.5 atmospheres, or about 0.1 to 0.2 atmospheres. In another approach, the conduit joints are cured under pressure during a rolling process similar to that described above. In this approach, conductive joints can be cured at a temperature of, for example, about 140 ° C to 170 ° C, and under a pressure of, for example, about 0.1 atmospheres to 1.0 atmospheres, or about 0.3 atmospheres to 1.0 atmospheres, or about 0.5 atmospheres to 1.0 atmospheres. Generally, the higher the temperature at which the epoxy cures, the more conductive the bond is.

In some variations, the substrate and / or one or more delamination layers placed underneath a serially connected string of superimposed solar cells are configured to have a shape-fitting surface to the underside of the string in a shingle fashion. of cells

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DI THE PMJFUpAD iNnwriMAL solar. For example, a metal substrate may be patterned to have a surface with a sawtooth cross section that conforms to the shape of the underside of the chain in a solar cell shingle fashion. In addition to or alternatively, one or more dielectric sheets positioned between the substrate and the solar cells can be accommodated or patterned to provide such a fitting surface. For example, such dielectric sheets can be overlaid in a shingle pattern that provides a top surface that conforms to the underside of solar cells in a shingle fashion. Supporting the string in a solar cell shingle fashion with an adjusting support surface can improve thermal contact between the solar cells and the substrate.

Solar energy collectors comprising the series connected strings of superimposed solar cells as described herein may preferably be oriented with the exposed edges of the solar cells (eg edges 12 in Figure 3A) away from the equator. . With solar cells in a shingle fashion oriented in this way, incident solar radiation on the cells will illuminate only the top surfaces of the cells, not the exposed edges. This can increase efficiency

IMPI ^ twsrrtvro muucanc. -, -,,, ·, VA ΜΟΠίρΛΓ with which the collector converts the radiation¹incident in electrical energy, because¹ ha i adrae / rón solar incident on the exposed edges of solar cells may not be efficiently converted to electricity.

The performance characteristics of solar cells can vary between solar cells even though the cells have essentially identical designs. Therefore, two solar cells of identical design that are illuminated identically can produce currents of two different magnitudes. In a string of solar cells connected in series, however, all cells must handle an identical current. Mismatches between cell performances in the chain decrease the overall efficiency of the chain. This problem can be easily dealt with with series connected strings of overlapping solar cells as described in this document. In any of the variations described above, the area of ​​each solar cell not overlapped by adjacent solar cells can be selected to match or substantially match the electrical performance (e.g., current) of all other solar cells. In the chain. That is, the overlap between adjacent cells can be adjusted to vary the illuminated area of ​​each solar cell such that the electrical performance of each solar cell is substantially adjusted with ₉3 IMPI ^^

INSTITUTO MEXICANO «LArtowtOAr CsMr &lt;yM&gt; ds ^ INDI&gt; mt Al -el of the other solar cells. This can improve the overall efficiency of the chain.

This disclosure is illustrative and not limiting. Additional modifications will be apparent to those skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.

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Having described the present invention as above, it is considered as a novelty and, therefore, the content of the following is claimed as property: