Method and manufacturing of sealed monolithic photoelectrochemical systems and a sealed monolithic photoelectrochemical system

(54) NAME Method for the manufacture of sealed monolithic electrochemical systems and sealed monolithic electrochemical systems (56) PUBLICATIONS REFERRED TO: - - () Method of manufacture of sealed monolithic electrochemical systems, the method comprising the following method steps:

application of electrolyte to a pattern of porous structure located on a substrate, which structure constitutes a monolithic electrochemical electrode and comprises a working electrode, an insulating layer and a counter electrode

application of a sealing material surrounding said porous structure to form a laminate comprising front plane consisting of said substrate and porous structure and a back plane consisting of the sealing material.

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The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code.

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SUMMARY

Method of manufacturing sealed monolithic electrochemical systems, which method comprises the following method steps:

applying electrolyte to a pattern of a porous structure located on a substrate, which structure constitutes a monolithic electrochemical electrode and comprises a working electrode, an insulating layer and a counter electrode

application of a sealing material surrounding said porous structure to form a laminate comprising front plane consisting of said substrate and porous structure and a back plane consisting of the sealing material.

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TECHNICAL FIELD

The present invention relates to a method for manufacturing sealed monolithic electrochemical systems according to the preamble of claims 1 and 18.1, in particular, to a method for producing monolithic electrochemistry systems comprising a substrate, a pattern on a substrate of a porous structure including a working electrode. an insulating layer and a counter electrode where the porous structure is filled with electrolyte before the pattern of the porous structure is encapsulated between substrate and a backing consisting of a sealing material.

Furthermore, the present invention relates to a sealed monolithic electrochemical system according to the preamble of claim 16.

BACKGROUND OF THE ART

WO97 / 16838 discloses a method for producing monolithic photoelectrochemical cells. In this method, photoelectrochemical cells are formed by applying patterns of conductive material to an electrically insulated translucent material. Then, a porous structure is applied by successive application of a layer of a porous semiconductor, a layer of a porous insulator and a layer of a porous conductor. After applying the porous structure, a liquid electrolyte is added to the porous structure. Furthermore, the porous structure is covered by an insulating cover layer.

However, it has been found that a number of problems arise when sealing monolithic electrochemical systems. First, it has been found that the cells are sensitive to moisture and contaminants since the presence of moisture and contaminants significantly affects the long-term stability of the system. Second, it is important to seal along the cells

1 68FH / ΙΠ, Μ.Π ;;: · lb outer edge effectively prevents leakage or dissipation of electrolyte from inside the cells as well as contamination and moisture from the outside into the cells.

In order to seal monolithic electrochemical systems, where electrolyte is in place at sealing, various methods have been tried, such as bonding and joining by pressing between two rollers. None of the methods tested to date have resulted in electrochemical systems with sufficiently good long-term properties and with a sufficiently low degree of deterioration of cell performance in the sealing process, which has also made industrial cost-effective production of electrochemical systems difficult.

BRIEF DESCRIPTION OF THE INVENTION

The objects of the invention are to provide a method for manufacturing sealed monolithic electrochemical systems where the risk of moisture and contamination in the cell after sealing is reduced, where the long-term stability of the cells increases and where the sealing exhibits a high degree of density against the environment.

These objects are achieved by a method according to the characterizing part of claim 1. The sealing material comprises a plastic which is melted and bonded to a front plane consisting of a substrate and cells located on the substrate. By heating and compressing the sealing material, a seal is obtained along the edge of the pattern of the porous structure. By the border is meant the inner border separating the different cells in a group of cells from each other, and the outer border separating a group of cells from the environment. Since the plastic layer is very flexible in its heated state, a very dense and good seal is obtained, whereby the risk of moisture and contamination penetrating decreases, thereby increasing the long-term stability of the system. Furthermore, the sealing method according to the invention reduces the risk that the cells' performance decreases during the manufacturing process.

In a preferred embodiment of the invention, the monolithic electrochemical system is exposed to vacuum, allowing evacuation of moisture and gases from the porous structure. This results in a cleaner and thereby a more long-term stable product can be obtained.

In a preferred embodiment of the invention, the front plane and the back plane are compressed

521 6G3 a flexible press tool. By compressing the front and back planes with a pliable pressing tool, a good seal is provided along the edge of the applied pattern of cells. The good seal is provided both along an inner stripe between the individual cells and an outer stripe surrounding the cells. The sealing between the cells, ie the inner edge, reduces the risk of leakage between the cells and the seal around the pattern of cells, ie the outer edge reduces the risk of penetration of dirt and moisture to the cells from the environment.

It is a further object of the invention to provide a sealed monolithic electrochemical system comprising effective barrier to moisture and environmental contamination from the cells, where the risk of degradation of the cell's function upon encapsulation is reduced and allows the cells to exhibit sufficiently long-term properties. These objects are achieved by a sealed monolithic electrochemical system according to the characterizing part of claim 16. By using a sealing material which comprises at least a first layer consisting of a plastic film, a joint between the front and the back plane of the electrochemical system is provided which reduces the risk of moisture entering the cells and reduces the risk of electrolyte flowing from a cell and contacting a cell. nearby cell. As the plastic layer is very flexible in its heated state, a very dense and good seal is obtained whereby the risk of moisture penetration decreases and thereby the long-term stability of the system increases.

In a preferred embodiment, the sealing material comprises at least one second layer which is a barrier layer and provides suitable properties to block the penetration of dirt and moisture from the environment to the cell. This type of sealing material is particularly suitable as the risk of deterioration of the long-term stability of the system is reduced.

DESCRIPTION

The invention will be described below with reference to the accompanying drawings, in which Fig. 1 is a sectional view of a sealed monolithic electrochemical system comprising a plurality of cells; Fig. 2 shows a second embodiment of a monolithic electrochemical system in which serial coupling between a number of cells is carried out alternately. coupling of ends.

Fig. 3 shows a set of cells applied to a substrate; Fig. 4 shows a flowchart for the sealing process of the monolithic electrochemical system; Fig. 6 shows a soft pressing head; Fig. 7 shows a two-chamber system for compressing an electrochemical system; 8 Figure 9 shows an electrochemical system with two-part sealing material, and Figure 9 shows an electrochemical system with outer regions strongly compressed.

DESCRIPTION OF EMBODIMENTS

In Figure 1, a sealed monolithic electrochemical system 1 comprising a plurality of cells 2A, 2B, 2C is shown in section. Each cell 2A, 2B, 2C is a porous structure and comprises a working electrode or photoelectrode 6, an insulating layer 7 and a counter electrode 8. The cells 2A, 2B, 2C or the porous structures are applied to a substrate in a pattern. The pattern is enclosed by a stripe, which is an inner stripe that separates the individual cells from each other and an outer stripe enclosing a group of cells which make up said pattern. An example of such a system is described in WO 97/16838, the description of which is incorporated in its entirety in this specification.

521 6:, 3 -η · ·, ··. ·. The monolithic electrochemical system 1 comprises working electrodes in the form of nanoporous photoelectrodes 6 built on a substrate. The substrate comprises a support layer 3 of fully or partially transparent material and a thin conductive layer 4 applied to the support layer 3. The support layer 3 may be made of glass or plastic, in which case the photoelectric system may be formed somewhat flexibly. Each photo electrode 6 is placed on the thin conductive layer. The conductive layer is divided into a pattern of thin dividing lines where the conductive layer is removed, forming a set of cells isolated from each other. The pattern preferably consists of a set of elongated rectangles, but can of course be formed in any way, but preferably in some surface pattern. An example of a suitable pattern is shown in Figure 2 which shows an electrochemical system 2 seen from above.

According to the embodiment shown in Figure 2, the pattern of the porous structure is shown as a set of rectangular cells 2A - 2D. The cells are placed long side by side. In this case, the outer edge is formed by a rectangle 40 enclosing the set of cells and an inner edge of a set of parallel lines 41 which separate the cells from each other. A group of cells is connected in series in some known manner, for example as indicated below. Other surface-covering patterns are also conceivable, such as a set of hexagons. However, the preferred embodiment with rectangles allows for simple serial coupling between cells. In order to provide serial coupling between cells in a simple manner, the layers of the cell are arranged in the embodiment shown in Figure 1 where cells are connected side by side as follows: The photo electrode 6 extends to one edge of the conductive layer 4 of the cells because a second edge be released. The dividing lines 5 are formed such that the photoelectrode does not run the risk of coming into contact with a nearby cell.

The photoelectrode 6 is covered by a porous layer of an insulator 7 which extends over an edge of the conductive layer and which isolates the photoelectrode 6 from a porous counter electrode 8 located on the insulator 7. The insulator 7 may preferably also constitute a diffuse reflector which reflects light that has passed the photoelectrode 6 without being absorbed in it, thereby increasing the absorption rate of systems.

In a preferred embodiment, the counter electrode 8 is applied in such a way that it essentially covers the insulator 7 and extends up to the layer not covered by insulator 7 on a neighboring cell. In this way, serially connected cells are created, whereby contacting 11,12 need only be applied to the first and last of a connected group of cells.

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The counter electrodes 8 of the respective cells are separated by a space 9. It is important that the cells are isolated from each other so that the electrolyte cannot leak out from the electrodes or isolator and make contact between electrodes in different cells. To ensure that this does not happen, the gap can be filled with an insulating material. In a preferred embodiment, this insulating material is comprised of portions of the sealing material 10 which is pressed into the gap 9.

Prior to closing the electrochemical system 1, an active agent, such as a light-absorbing dye or an electrochromic material, is adsorbed to the photo electrode 6. Further, electrolyte is applied to the porous structure consisting of photoelectrode 6, insulator 7 and counterelectrode 8. In a preferred embodiment, printing process, preferably screen printing. By this method, the right amount of electrolyte can be supplied so that the porous structure of each cell is filled but does not become overcrowded. If too much electrolyte is supplied, there is a risk that the electrolyte will run out in the gap 9 between each cell, leaving the risk of short-circuiting between the cells. In a second embodiment, the electrolyte is supplied by allowing the porous structure to adsorb electrolyte during a dispensing process.

In a second embodiment, shown in Figure 3, serial coupling is performed between a number of cells 2A, 2B and 2C by connecting existing ends of the cells as will be described below. In this embodiment, the cells are in a pattern where each cell is rectangular and has two long sides and two ends. The cells are formed on a substrate with a layer 4 of conductive material. The cells are isolated from each other by etching paths of the conductive material. Each cell comprises an anode 6 of porous material, this anode being, where appropriate, a photosensitive photo electrode. On the anode 6, an insulator 7 of porous material is applied. A counter electrode 8 of porous material is applied to said insulator 7. In order to provide serial coupling between the cells, the cells are coupled so that the anode of one cell is coupled to the counter electrode of the next cell. In the embodiment shown in Figure 2, this is accomplished by forming the etched webs 5 in a zigzag pattern which generates an L-shaped pattern of conductive surfaces consisting of a set L, having a back 13 and a foot 14 facing each other so that the projection from one L can be placed directly adjacent to the next L. The photo electrode 6 is completely placed within the back of an L shaped area, ie the elongated portion. The insulator 7 is positioned so that it covers the photoelectrode and extends slightly into the foot 14 of the L-shaped region of an adjacent cell, i.e., the insulator 7 bridges the etched web 5 within a region corresponding to the width of the cell. The serial connection is accomplished through

521 603 that the counter electrode 8 of a cell is allowed to extend into the conductive layer 4 of a neighboring cell. In the embodiment shown in Figure 3, this is accomplished by the counter electrode 8 extending into the foot 14 of an L-shaped region of a neighboring cell. Figure 3 also shows an encapsulating material 10A and a cover layer 10B together constituting a sealing material 10.1. In a preferred embodiment, the encapsulating material 10A is an adhesive layer 19A and the cover layer 10B is an adhesive layer 19B and a barrier layer 19C.

After the electrolyte has been added to the porous structure, the electrochemical system 1 is sealed by means of a sealing material 10 according to the invention by a method described below in connection with Figure 4.

In a first method step 20, a sealing material 12 is applied to the substrate 3 in such a way as to completely cover cells 2A - 2C and its porous structure to form a sealed monolithic photoelectric system comprising a front plane consisting of said substrate and the porous structure, and a backplane consisting of the sealing material The sealing material comprises at least one layer of plastic, preferably a thermoplastic such as, for example, methacrylic acid polyethylene, which is intended to adhere to the underlying substrate and optionally the porous structure located on the substrate upon heating. In a preferred embodiment, the sealing material is a laminate in which a plastic adhesive layer and a barrier layer with low or no air and liquid permeability, for example an aluminum foil. In a further preferred embodiment, the sealing material comprises, on the one hand, a plastic adhesive layer which is intended to abut against the substrate, as well as a laminate consisting of a plastic layer and an aluminum layer where the plastic layer is intended to adhere to said adhesive layer. The plastic layer is adhered to the aluminum layer in a manner well known to those skilled in the art, for example by gluing. The use of an intermediate layer provides a good joint because the more flexible adhesive layer is more effective than the less flexible aluminum layer assumes the shape of the substrate.

In order to ensure that sufficient density against liquid penetration through the edge of the adhesive layer is obtained, the adhesive layer is formed in a preferred embodiment having a thickness of less than 50 µm and in a further preferred embodiment having a thickness of less than 30 µm. With said thicknesses, a layer is obtained which is sufficiently thin that the edge flow does not adversely affect the long-term stability of the enclosed cells, while the thickness is sufficiently large to be easily manageable.

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In a second method step 21, the sealing material is compressed with the substrate and the cells located on the substrate. The sealing is done by compressing a front plane consisting of said substrate and the porous structure and a back plane consisting of the sealing material, whereby the adhesive layer merges with the front plane, permitting sealing along the edge of the pattern. This seal insulates the individual cells from one another along the inner edge of the pattern, thereby preventing electrolyte leakage between the cells, and isolates the group of cells that make up a pattern from the outer edges of the pattern, thereby preventing dirt or moisture from entering the cells. Below are alternative preferred embodiments of the compression.

Furthermore, in Figure 4A, some preferred subprocesses are shown below the seal 21.

In a first subprocess 22, first, a plastic adhesive layer is placed against the front plane, and above that a laminate consisting of an adhesive layer, preferably of plastic and a barrier layer, preferably of aluminum. In case a plastic layer and an aluminum layer are used, the plastic layer is adhered to the aluminum layer in a manner well known to those skilled in the art, for example by gluing. The use of an intermediate layer provides a good joint because the more flexible adhesive layer adapts more effectively than the less flexible aluminum layer to the shape of the substrate. In Figure 8, front plane 19 shows adhesive layer 19A and barrier layer of adhesive layer 19B and barrier layer 19C. The adhesive layer 19B has the function of joining barrier layers 19C and adhesion layer 19A. The adhesive layer is preferably a thermoplastic.

In a second subprocess 23, the front plane and the sealing material are exposed to a vacuum, whereby the presence of dirt and moisture in the cells can be reduced.

In a third subprocess 24, the front plane and the sealing material are compressed with a compliant pressing tool, whereby good sealing around both inner and outer stripes.

In addition, in order to obtain a further better closure around the outer edge, the outer edge, on a piece slightly outside the cells, for example 2-5 mm from the cells edge, can be compressed with a hard pressing tool in a fourth subprocess 25. This compression thins any adhesive layer 19A, whereby the risk of penetration of dirt and moisture from the environment after joining is reduced. Figure 9 shows a group

521 Cells which are compressed with a hard pressing tool within two regions 26A and 26B, essentially enclosing a grouping of cells 2A - 2D. In a region 26C, 26D around each of the contacts 11,12, the cell array is not compressed to avoid the aluminum layer in the barrier layer being compressed with the conductive layer on the substrate.

In order to ensure that any transitions between conductive bearings and aluminum layers in areas 26A and 26B do not adversely affect the cell grouping, these areas are separated by etched paths 26E and 26F, the areas where hard pressing is electrically insulated from the cell grouping in general.

The above-mentioned sub-processes can be combined individually to obtain various preferred embodiments of the invention.

In a preferred embodiment, the compression takes place with a pliable pressing tool. By a compliant pressing tool is meant that the pressing tool is allowed to deform sufficiently to allow the pressing tool to be deformed for access in the spaces between the cells, the sealing material being pressed against the front plane so that the sealing material is pressed against the cells and down into the spaces between the cells and around the edges of the pattern. Figures 5, 6 and 7 show examples of embodiments of compliant pressing tools.

In Figure 5, compression of a monolithic photoelectric system is shown by means of a flexible membrane 15A. The electrochemical system 1 is placed on a substrate 15B after which it is covered by the flexible membrane 15 A. The flexible membrane may conveniently be made of rubber. Thereafter, the electrochemical system is exposed to a pressure through the membrane 15A and heat is supplied thereby providing sealing. In a preferred embodiment, the pressure on the membrane 15A is achieved by exposing the space 16 around the electrochemical system 1 to negative pressure. This suppression reduces the occurrence of moisture and contamination in the cells before closure, which results in better quality of the cells. The substrate 15B can also be designed as a flexible membrane.

In a preferred embodiment, compression takes place under pressure which is obtained from flexible membranes which enclose the monolithic electrochemical system. By using a flexible membrane, uniform pressure is obtained over the entire monolithic electrochemical system and good sealing is obtained in the above-mentioned space 9 between the cells.

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In a preferred embodiment, the pressure is obtained by placing the monolithic electrochemical system in a pocket between two flexible membranes and exposing said pocket to a negative pressure, whereby the ambient pressure compresses the monolithic electrochemical system. This suppression also contributes to reducing the moisture and dirt appearance of the porous structure before closure finally occurs.

In Figure 6, an alternative embodiment is shown in which the compression takes place with a press head 17 comprising a press surface 18 of soft material, for example rubber, whereby compression of the sealing material against the front plane is allowed so that the sealing material is pressed against the cells and down into the spaces between the cells and around the edges of the pattern. According to a preferred embodiment, this type of pressing can take place in a chamber exposed to vacuum, whereby the presence of dirt and moisture of the finished product can be reduced.

In one embodiment, the monolithic electrochemical system is placed in a heating furnace which heats the monolithic electrochemical system to about 100 ° C, where heating from room temperature takes place for about 30 minutes. The material is then cooled slowly.

According to an alternative method, the electrochemical system is sealed by placing the phonon plane and the sealing material in a chamber which is exposed to a vacuum. In order to allow the evacuation to reduce the occurrence of dirt and moisture further, in accordance with a preferred embodiment, the ffont plane and sealing material are separated by a gap during a period of exposure of the vacuum.

When the front plane and sealing material have reached the correct temperature, the ffont plane is compressed with the sealing material.

In one embodiment of the invention, compression is effected by utilizing a two-part chamber as shown in Figure 7. The chamber 30 is formed in a housing 31 and comprises a first and a second sub-chamber 34, 35 separated by a flexible membrane 32

521 683 // the sub-chambers are placed the electrochemical system 33 to be joined. To the cam is an air pump (not shown) connected or connectable to enable evacuation of both the first and second sub-chambers. For this purpose, the housing 31 may be provided with a communication channel between the first and second chambers where the communication channel comprises a check valve located so that evacuation of the first and second chambers can be done jointly, but that air does not flow from the second to the first chambers when air is later introduced to allow compression of the electrochemical system's front plane and sealing material.

The invention is not limited to the above described embodiments but can be varied within the scope of the following claims. For example, the electrochemical system may consist of both a photoelectrochemical system ie. a solar cell, or a display where the elements, for example, constitute letter segments. In one embodiment, it is conceivable to encapsulate a display next to a solar cell. In this case, different electrolytes will be used for the display and the solar cell, which are encapsulated simultaneously. Further, both the backplane and the frontplane may comprise additional layers, for example, a colored layer may be placed between adhesive layer 19A and adhesive layer 19B to give the desired appearance, alternatively these or other layers included in the product may be colored.

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