Semiconductor photoelectric converter and method for manufacturing thereof

The invention relates to the technique of converting the energy of solar radiation into electricity, in particular, to the construction of contacts and to the chemical composition of materials, used in the manufacture of current and semiconductor elements of the photovoltaic converter.

The composition and manufacturing technology of thin film of hydrogenated polycrystalline silicon semiconductor with average crystalline sizes smaller than 10 nm containing more than 50% crystalline phase are known [1].

The disadvantage of this film is that it contains up to 40% of amorphous silicon, which reduces the energy efficiency of the converter and creates the need to properly increase the irradiated surface of the semiconductor in order to increase the current intensity to the maximum possible values. .

Thick film contact between the crystalline silicon semiconductor and the conductive electrodes is also known! current, consisting of paste with silver content, applied on both sides of the semiconductor and thermally processed, coated on the back with a soldering iron based on a mower, and on the illuminated part - with a solder alloy and nickel coating [2].

The disadvantage of this contact is that the use of flux during seaming and bonding leads to its leakage on the working surface of the semiconductor, its partial shielding, the decrease of the active surface, the decrease of the energy efficiency of the cell. The use of nickel to cover the thin current collector bands increases their electrical resistance and leads to an additional consumption of electricity produced by heating the semiconductor, and the use of prefabricated current collectors complicates the manufacturing process and reduces the reliability of the converter.

The closest solution is the semiconductor photovoltaic converter, which confines о the semiconductor plate, on the back surface of which a solder-lead solder layer is applied, and on the front surface silver and nickel current metal collector contacts are applied. (or titanium) and an organosilicon adhesive layer, by means of which the plate is secured with a protective glass coating, on which a hydrophobic film is applied. The glass used is made with the possibility of forming an electric field inside the action of ionizing radiation [3].

The disadvantages of this converter are: use of the flux during the seaming of the back surface of the semiconductor plate, which subsequently leads to incomplete use of its active surface, to the decrease of the contact surface of the semiconductor crystals with the solder alloy due to the penetration of the flux into the recesses and the shielding thereof of a portion of the real surface of the semiconductor nanocrystals, which when used in photo-effect could increase the electrical conductivity of the transition layer and the energy efficiency of the photovoltaic converter. The use of the polycrystalline silicon plate with partially oriented crystallographic planes results in the decrease of the current efficiency of each unit of volume of the semiconductor material. The application on the front of the photovoltaic converter of the paste with silver content in the execution of the narrow current collecting bands is also related to the dirt and the shielding of a portion of the work surface of the plate with the binder substances, the reduction of its optical clarity and the worsening of the photoeffect results. The use of the hydrophobic protective glass reduces the output power of the photovoltaic converter, according to the experimental results, at least by 17 ... 20%. Creating with the help of metallic glass the protection of the electric field, which brakes the electrons, leads to the decrease of the energy of the solar rays and the specific power of output.

The problem solved by the invention consists in increasing the energy efficiency of the photovoltaic converter by 1.5 times.

The semiconductor photovoltaic converter, according to the invention, removes the abovementioned disadvantages by confining a semiconductor layer, on the front surface of which current collector metal contacts and an organosilicon adhesive layer are applied, and on the opposite surface of the semiconductor layer a layer is applied. of others to be soldered. At the same time, the semiconductor layer is made of silicon nanocrystals, whose crystallographic planes are oriented in one direction. Soldering alloy based

MD 4377 Cl 2016.05.31, the mower contains a stack of 3 ... 4% of the alloy mass. The current collector contacts are made of galvanic iron-cobalt or ferrocadmium alloy, and the protective layer of organosilic adhesive with the thickness of 0.17 ... 0.2 mm is applied on all surfaces of the converter.

The process of manufacturing the semiconductor photovoltaic converter, according to the invention, removes the disadvantages mentioned above by orienting the silicon nanocrystals by rotating an external electrostatic field source around the semiconductor layer with the rotation step of 10 ° and experimentally determining the angle below which fix the external electrostatic field source, melt the solder alloy film on the basis of an alloy mower base, the silicon nanocrystals oriented with the concomitant alloying of a part of the nanocrystals with the stub are deposited in the alloy and the alloy is cooled. The obtained plate is immersed in a galvanic bath with electrolyte, which confines aqueous solution, for example, of iron chloride salt - 360 g / L, cobalt sulphate - 40 g / L at pH = 1,2 ... 1 , 7 and 313K solution temperature, to ensure the durability of the galvanic alloy adhesion with the semiconductor up to 220 g / mm² of the contact surface, the anodic treatment of the frontal surface of the semiconductor layer is performed within 25 s at the amplitude density of the current of 55 ... 60 А / dm², a template of the front surface cleaned of oxides and impurities of the obtained plate is fixed, the plate is connected with the cathode to a periodic current source with a return pulse adjustable according to amplitude and duration, and to the ratio of the cathodic and anodic impulse amplitudes. current equal to 6: 1, within 3 minutes the direct pulse density increases from 0 to 40 А / dm², the galvanic alloy is deposited within 12 to 20 minutes at the established ratio of currents. The obtained photovoltaic converter is washed with distilled water at -330K, dried, immersed in organosilic adhesive, removed from the vessel with adhesive and dried in the drying cabinet at 360K for 10 minutes.

The use of the proposed construction of the semiconductor photovoltaic converter allows to increase the energy efficiency of the conversion process from the technical result: improving the electrical contact between the solder alloy layer and the silicon nanocrystals and their co-cooling; electrochemical anodic treatment of the frontal surface of the semiconductor layer with a periodic current with a return impulse adjustable by amplitude and duration; obtaining the galvanic alloy in the regimes, which ensures the high durability of the adhesion of the galvanic alloy with the semiconductor layer; formation of the protective layer from organosilic adhesive; the use of new current conducting materials for the anode and cathode.

Experimentally it was found the possibility of increasing the current in the outer circuit by 1.5 times by changing the direction of orientation of the crystallographic planes of the silicon nanocrystals in relation to the direction of the light flux by rotating the external electrostatic field source, and by modifying the chemical composition of the anode material. and the cathode - the possibility of increasing the electromotive voltage by ~ 250 mV. The data obtained were used to increase the energy efficiency of the semiconductor photovoltaic converter. These results are confirmed experimentally in the process of testing the variants of construction and execution of photovoltaic converters. With struct! the maximum possible current has been obtained m the outer circuit of the photovoltaic converter, the conditions for obtaining a resistant connection between the electrical contacts and the silicon nanocrystals through the fusion of the modified solder alloy and the deposition of the galvanic alloys have been found to ensure the lasting conductive contacts.

The semiconductor photovoltaic converter confines an anode, made of the solder-based solder alloy, which confines the stubium in the amount of ~ 4% of the mass of the alloy, the semiconductor layer of silicon nanocrystals with dimensions of about 40 nm, a thick cathode, executed in shape of current collecting strips with a thickness of 0.17 ... 0.2 mm, which leads to the compensation of the ohmic losses, the increase of the durability and the hardness of the semiconductor layer, and for the cathode execution alloys with the internal bond between electrons and their nuclei of atoms are used more powerful.

The procedure is performed as follows.

The silicon nanocrystals are oriented by rotating an external electrostatic field source around the semiconductor layer with the rotation step of 10 ° to determine the maximum possible current in the outer circuit m given conditions. The angle between the vertical axis and the intensity vector of the electrostatic field is determined experimentally

MD 4377 Cl 2016.05.31 exterior, below which the external electrostatic field source is fixed, melts the solder alloy film based on a tin alloy base, it is deposited in the silicon nanocrystals oriented with the concomitant alloying of a part of nanocrystals with I choked and cooled the alloy. On the back and side surfaces of the obtained plate, a layer of organosilic adhesive is deposited, after which the plate is inserted in the drying cabinet and dried. The obtained plate is immersed in a galvanic bath with electrolyte, which confines aqueous solution of iron chloride salt - 360 g / L, cobalt sulphate - 40 g / L at pH = 1,2 ... 1,7 and temperature 313K solution, to ensure the adhesion of the galvanic alloy with the semiconductor up to 220 g / mm² of the contact surface, the anodic treatment of the frontal surface of the semiconductor layer is performed within 25 s at the amplitude density of the current of 55 ... 60 А / dm². From the front surface cleaned of oxides and of impurities of the obtained plate, a template is fixed, the plate is connected with the cathode to the о periodic current source with adjustable return pulse after amplitude and duration, and at the ratio of cathode and anodic pulse amplitudes of current equal to 6: 1, within 3 minutes the direct impulse density increases from 0 to 40 А / dm², to ensure a strong connection between the electrical contacts and the silicon nanocrystals, after which the galvanic alloy is deposited within 15 minutes at the established ratio of currents. The obtained photovoltaic converter is washed with distilled water at -330K, dried, immersed in organosilic adhesive, removed from the vessel with adhesive and dried in the drying cabinet at 360K for 10 minutes.

Subsequently, the photovoltaic converter is tested by irradiating it with radiated soil.

The proposed invention allows: increase of the internal electromotive force between the electrodes by moving the anodic potential proper to the electropositive and the cathodic side - towards the electronegative side, increasing the maximum possible current of the semiconductor converter by orienting the silicon nanocrystals in an external electrostatic field, increasing the potential difference between the anode and by using galvanic alloys with high values ​​of the potentials of zero surface charge, increasing the intensity of the internal electric field of acceleration, doping a part of nano- crystals with an abutment, decreasing the output of the electrons from the tin-based solder alloy with 0.163 eV by doping it with an abutment, increasing the contact surface of silicon nanocrystals with metals the anode and the cathode, the reduction of the contact resistance at the separation limits of the alloy and the nanocrystals surfaces, the creation of an internal electric field in the semiconductor layer, which accelerates the free charges, the use of galvanic alloys, which ensures the resistance of the bond with the silicon nanocrystals, whose surfaces have a potential increased by zero charge and increased values ​​of the electron output work up to 4.72 eV.

Example

For the laboratory tests, a photovoltaic converter was manufactured: one according to the invention, another - according to the nearest solution.

For the manufacture of the photovoltaic converter, a square steel frame was used, the size of an inner side of which was 100 mm. Two rows of supports were fixed on two opposite sides of the interior frame. On the top brackets was installed a о quartz glass with a thickness of 3 mm, and on the bottom row - a melting device, powered by a laboratory transformer. The outer part of the frame (in the middle part of it) was rigidly fixed by a support with the possibility of rotating the frame to establish the required horizontal position of the quartz glass by means of a level meter.

On the quartz glass was placed a film of solder-based solder (tin-lead) with a thickness of 150 µm alloyed with a stub in the amount of 4% by weight of the alloy. On the surface of the film was coated a layer of silicon nanocrystals with dimensions of about 40 nm, the thickness of this layer was 3 ... 4 mm. From the other side of the frame (opposite the support) was installed another support, from whose free end was fixed a steel slide bearing, with о ceramic vertical bar with dimensions of 15χ50^χ120 mm. The upper and lower sides of the bar symmetrically with respect to the axis of rotation have been fixed horizontally two insulated boards with dimensions of 110x125 mm. One of the plates was connected to the positive pole of a potentiostat, and the second - to the negative pole. The applied voltage was set from 110 to 240 V from

MD 4377 Cl 2016.05.31 laboratory autotransformer. The rapporteur was fixed by the fixed support, and by the movable bar - an indicator of the rotation angle.

Above the frame with silicon nanocrystals was placed the plate, connected to the positive pole, and below the frame - the plate, connected to the negative pole, in compliance with the alignment. From the reflector of a lamp with a power of 12 W, the ray of light was directed on the silicon nanocrystals with constant intensity. The solder alloy film was connected in series by a flexible copper conductor with a resistor of 10 Ω and with a millimeter or microameter, connected to a portable grid-cathode, executed in the form of a current conductor template.

To identify the position of the nanocrystals, where the current in the inner circuit is maximum, the source of external electrostatic field, and respectively the external electrostatic field with constant intensity rotates around the semiconductor layer with the rotation step of 10 °. The current value was set when the template contacts the silicon nanocrystals.

When establishing the maximum current in the external circuit, the fmal value of the angle between the vertical axis and the rotation angle indicator, directed in the opposite direction of the intensity vector of the electrostatic field, was determined. After determining the angle equal to 40 ... 50 °, the film of solder alloy, placed horizontally on the quartz glass, was melted, the oriented silicon nanocrystals were deposited in the alloy, after which the alloy cooled. A plate with a thickness of about 280 gm was obtained, with a total thickness of 2 mm.

The back surface of the obtained plate was coated with the organosilic adhesive and dried. On the galvanic fontal surface of the electrolyte, which contained 360 g / L of FeCl₂and 40 g / L of CoSO₄ with pH = 1.2, an iron-cobalt alloy was deposited. In the electrochemical process, an impulse return current was applied according to amplitude and duration (see SU 944031 Al 1982.07.15). Prior to deposition anodic treatment of the front surface of the semiconductor layer was performed within 20 s at the current density of 60 А / dm² with return pulse disconnected. A template was fixed to the front surface cleaned of oxides and impurities of the obtained plate. Within 3 minutes the direct impulse density was increased from 0 to 40 А / dm² (output in the operating mode) and through the template was made the cathodic deposition of the alloy within 20 minutes at the ratio of the amplitudes of the cathodic and anodic impulse currents equal to 6: 1, the cathodic current density of 42 ... 45 А / dm³ and electrolyte temperature of 313K. The thickness of the deposited layer was 180 ... 190 gm. After the completion of the alloy deposition process, the obtained photovoltaic converter was washed with flowing distilled water and dried in a room at a temperature of 333K, after which it was tested: without charge and with 10 Ω load. The photovoltaic converter obtained was immersed in organosilic adhesive within 90 s, removed from the adhesive vessel and dried in the drying cabinet at 360K for 10 min.

Comparative tests of the semiconductor photovoltaic converters were performed on irradiation with solar ionizing radiation.

The test results showed that the specific power of the claimed photovoltaic converter exceeds the specific power according to the nearest 2.4 times glass solution and without 1.7 times the glass.

MD 4377 Cl 2016.05.31 (56) Bibliographic references cited in the description:

1. RU 2227343 C2 2004.04.20

2. RU 2303830 C2 2007.07.27

3. RU 2144718 Cl 2000.01.20 (57) Claims: