Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
  • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
  • H01L31/0745—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
  • H01L31/0747—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer or HIT® solar cells; solar cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0224—Electrodes
  • H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0224—Electrodes
  • H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
  • H01L31/022483—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers composed of zinc oxide [ZnO]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0236—Special surface textures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0236—Special surface textures
  • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0236—Special surface textures
  • H01L31/02366—Special surface textures of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
  • H01L31/056—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means the light-reflecting means being of the back surface reflector [BSR] type
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/52—PV systems with concentrators
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/958—Passivation layer

Definitions

• the present invention relates to a photovoltaic cell comprising a semiconductor substrate, an emitter formed by a layer having a first conductivity (p or n), a front passivation layer placed between the substrate and the emitter, a transparent conductive layer before , a rear passivation layer deposited on the rear surface of the substrate and a reflective element comprising a rear transparent conductive layer, a bonding layer and a reflective layer.
• a photovoltaic cell comprising a semiconductor substrate, an emitter formed by a layer having a first conductivity (p or n), a front passivation layer placed between the substrate and the emitter, a transparent conductive layer before , a rear passivation layer deposited on the rear surface of the substrate and a reflective element comprising a rear transparent conductive layer, a bonding layer and a reflective layer.
• It also relates to a method of manufacturing such a photovoltaic cell.
• the present invention relates to the field of photovoltaic cells, commonly called solar cells, which operate essentially on the following principle: when a photon arrives on a semiconductor, it modifies the number of charge carriers by passage of an electron from the valence band to the conduction band and produces an electron / hole pair. An electromotive force then appears at the terminals of the junction which behaves like a battery.
• photovoltaic cells Two ways are explored to make photovoltaic cells. One of them consists in using a material with high photovoltaic efficiency (greater than 10%) of a crystalline nature which is cut into platelets. The other is to deposit a thin layer a material with a lower yield (5% to 10%) on an inexpensive support (glass, stainless steel, plastic, etc.) of large dimensions.
• the present invention relates to the first route mentioned.
• a first method for producing such cells consists in doping a substrate formed of silicon, by thermal diffusion of an element such as boron or phosphorus, at a temperature higher than 1000 ° C.
• This process has a number of drawbacks. It requires a high temperature treatment which consumes a lot of energy and leads to a high manufacturing cost and moreover, if a thin substrate and a high temperature are used, the risk of folding or breaking of said substrate becomes high and the waste is important.
• the solar cells obtained according to this process are therefore relatively expensive.
• the cell comprises a silicon substrate of positive conductivity p on which a front layer of negative conductivity n and a passivation layer of silica (SiO.sub.) Are added.
• the passivation layer of silica is first deposited on the rear face of the substrate. Part of this passivation layer is then removed, and finally the positive conductivity layer doped with boron is deposited to form the rear contact by locally creating the surface field.
• the use of a passivation layer of silica necessarily involves the creation of non-passivated zones to make the rear contact.
• An embodiment has also been devised making it possible to increase the optical path of the light rays in a solar cell, while keeping the thickness of this cell as small as possible.
• This embodiment consists in providing the upper surface of the cell with a transparent layer, textured in such a way that the light rays which arrive on this layer perpendicular to the plane of the cell are deflected by refraction and pass through the cell in a direction in which its thickness is not minimal.
• Another method leading to the same result consists in using a textured substrate and in depositing on this substrate layers of substantially uniform thickness.
• a cell as defined in the preamble characterized in that the rear passivation layer covers the entire rear surface of the substrate, and in that said passivation layer is covered with a rear layer, producing a surface field, having a second conductivity (n or p) opposite to the first conductivity of the emitter.
• the semiconductor substrate can have said second conductivity (n or p), be intrinsic or be compensated.
• the semiconductor substrate can be made of crystalline or polycrystalline silicon and its thickness can be between 50 ⁇ m and 150 ⁇ m and preferably substantially equal to 80 ⁇ m.
• the emitter is advantageously formed from hydrogenated microcrystalline silicon or from hydrogenated silicon carbide. Its thickness is between 20 ⁇ and 500 ⁇ and preferably substantially equal to
• the front passivation layer is preferably made of intrinsic hydrogenated amorphous silicon and its thickness is advantageously between 20 ⁇ and 500 A and preferably substantially equal to
• said transparent conductive layer comprises zinc oxide (ZnO) and its thickness is preferably between 500 ⁇ and 5000 ⁇ and substantially equal to 1000 ⁇ .
• the rear passivation layer may be made of intrinsic hydrogenated amorphous silicon and its thickness is advantageously between 20 A and 500 A and preferably substantially equal to 80 A.
• the rear layer producing a surface field is advantageously made of hydrogenated microcrystalline silicon and its thickness is preferably between 100 ⁇ and 1000 ⁇ and substantially equal to 300 ⁇ .
• the rear transparent conductive layer is made of highly doped zinc oxide (ZnO) and its thickness is between 500 ⁇ and 5000 ⁇ and substantially equal to 2000 A.
• ZnO highly doped zinc oxide
• the bonding layer of the reflective element is preferably a layer of titanium (Ti) of thickness between 10 A and 100 ⁇ and substantially equal to 15 A and the reflective layer of this element is composed of silver and a a thickness substantially equal to 2000 . AT.
• the transparent conductive layers front and rear of the cell according to the invention can be textured and the substrate can be smooth.
• This substrate can also be textured and the transparent conductive layers front and rear can have a substantially uniform thickness.
• the method of manufacturing a photovoltaic cell according to the invention is characterized in that the following steps are carried out: - a semiconductor substrate is placed in a deposition chamber; - A plasma is deposited successively at a deposition frequency between 35 and 200 MHz and preferably substantially equal to 70 MHz, a layer of frontal passivation, an emitter, a layer of back passivation and a layer of back producing a field of area;
• a front transparent conductive layer and a rear transparent conductive layer are deposited by a magnetron sputtering method at a radio frequency between 1 and 100 MHz and preferably substantially equal to 13.56 MHz; and - a bonding layer and a reflective layer are deposited on the rear transparent conductive layer.
• the substrate which is placed in the deposition chamber, has undergone chemical attack.
• the substrate which is placed in the deposition chamber, is a raw substrate obtained after sawing, the front surface and the rear surface of which are attacked by means of a plasma at a frequency included between 1 and 200 MHz and preferably equal to 70 MHz.
• a textured transparent conductive layer is deposited on a substantially smooth substrate.
• the substrate is attacked by a plasma at a frequency between and between 1 and 200 MHz and layers of substantially uniform thickness are deposited on the textured substrate thus obtained.
• the whole of the operations is preferably carried out at a temperature between 20 ° C and 600 ° C and preferably between 150 ° C and 300 ° C.
• FIG. 1 is a schematic sectional view of a first embodiment of a photovoltaic cell according to the invention, obtained from a smooth substrate;
• FIG. 2 is a schematic sectional view of a second embodiment of a photovoltaic cell according to the invention, obtained from a textured substrate;
• FIG. 3 illustrates the steps of the manufacturing process of a photovoltaic cell according to the invention.
• the photovoltaic cell 10 essentially consists of a substrate 11, provided on one of its faces, with a frontal passivation layer 12, with an emitter 14 and with a transparent conductive layer 15 and on its other face, a rear passivation layer 17, a rear layer 18 producing a surface field and a reflective element 19.
• Light rays 16 arrive on the photovoltaic cell on the side of the front transparent conductive layer 15.
• the substrate 11 is made of crystalline silicon and in the embodiment described, has a thickness of about 80 ⁇ m.
• the front passivation layer 12 is obtained by depositing on the front face of this substrate, an intrinsic layer of hydrogenated amorphous silicon of thickness approximately 80 ⁇ . Then deposited on this front passivation layer 12, a microcrystalline layer of hydrogenated silicon of thickness about 100 A having a conductivity, called first conductivity which, in the example shown here, is a negative conductivity n.
• the layer thus obtained constitutes the emitter 14-.
• a transparent conductive layer 15 (for example made of zinc oxide ZnO) and having a textured surface obtained by chemical attack, by plasma, or by any other similar process, is then deposited on this emitter 14-.
• This transparent conductive layer 15 with an average thickness of 1000 ⁇ , taking into account its texture, constitutes a "light trap".
• the incident light rays 16 arriving perpendicularly to the plane of the cell 10 are deflected by refraction so that the actual length traveled by each ray in the cell is lengthened. This has the effect of increasing the number of band-changing electrons, and therefore the number of electron / hole pairs, and thus increasing the efficiency of the cell.
• this transparent conductive layer 15 can be made of any transparent conductor. Its thickness is chosen so as to constitute an anti-reflective layer for the range of wavelengths used. In the application described, the thickness is optimized for the solar spectrum.
• the rear passivation layer 17 deposited on the rear face of the substrate 11 is identical in composition and thickness to the layer 12.
• the rear layer 18 producing a surface field is obtained by depositing, on the layer 17, hydrogenated silicon, the conductivity, called second conductivity, is opposite to the conductivity of the emitter 14, and in this case, positive. The deposit is made over a thickness of approximately 300 A.
• the three layers constituting the reflecting element 19 are successively deposited on the monocrystalline layer thus obtained.
• the first layer 20 of this reflecting element is a transparent conductive layer which prevents light from inside the cell from coming out, returning it back into the cell through the two junctions.
• This transparent conductive layer 20 is composed of zinc oxide (ZnO) and has a thickness of 2000 ⁇ .
• a reflective layer is composed of zinc oxide (ZnO) and has a thickness of 2000 ⁇ .
• This reflective layer 22 also plays the role of rear contact element.
• the substrate 11 has a conductivity.
• This conductivity which must be opposite to that of the emitter 14, is a positive conductivity p. It should however be noted that a similar photovoltaic cell can be produced by reversing all the conductivities.
• the substrate then has a negative conductivity, as well as the microcrystalline layer 18 and the emitter 14 has a positive conductivity.
• the substrate can be compensated or intrinsic.
• Figure 2 shows an embodiment in which the substrate 11 'is made of a material identical to that of the substrate 11 of Figure 1, but has textured front and rear surfaces.
• the emitter 14 and the rear layer 18 producing a surface field are similar to those described with reference to FIG. 1.
• the transparent conductive layers front 15 and rear 20 also have a uniform thickness.
• the final surface of the finished cell is textured in the same way as in the cell shown in Figure 1.
• FIG. 3 represents the stages of the manufacturing process of a photovoltaic cell as described above.
• the substrate 11 is placed in a deposition chamber 30, on a support 31 allowing the two faces of this substrate to be exposed simultaneously to etching and deposition devices 32.
• the substrate introduced may have undergone before its introduction into the deposition chamber, a chemical attack according to a method known per se making it possible to remove the layers of material which have been damaged during its sawing. It can also be introduced as is.
• the first operation to be carried out consists in removing the deteriorated layer by carrying out a plasma attack at a frequency of approximately 13.56 MHz on both sides. of the substrate.
• the second step of the process is optional. It consists in attacking the substrate by means of a plasma at a frequency between 1 and 200 MHz. This attack makes it possible to obtain the texture of the surfaces of the substrate. This step is of course only carried out if one wishes to texturize the substrate and not the transparent conductive layers.
• the front passivation layer of intrinsic hydrogenated amorphous silicon is deposited on the substrate.
• This deposition is carried out according to the very high frequency plasma deposition method as described in European patent EP-A-0 263 788, this frequency preferably being of the order of 70 MHz.
• microcrystalline layer of hydrogenated silicon serving as emitter 14 is then successively deposited, the rear passivation layer of hydrogenated amorphous silicon and the rear layer 18 producing a surface field.
• a fourth step consists in depositing by a vaporization process known per se, such as a magnetron cathode sputtering process at a frequency equal to 13.56 MHz, the transparent conductive layer before 15 and the layers forming the reflecting element 19 - If the substrate is smooth, conductive layers with surface texturing will be deposited. On the other hand, if the substrate is textured, the conductive layers will be produced so as to have a substantially uniform thickness.
• a vaporization process known per se such as a magnetron cathode sputtering process at a frequency equal to 13.56 MHz
• This process has the advantage of making it possible to carry out all of the steps continuously without intermediate manipulation between the moment when the substrate is introduced into the deposition chamber, even when it is introduced there directly after sawing, and that when the cell is complete. This not only saves manufacturing time compared to conventional manufacturing processes in which the substrates must be handled during manufacturing, but also allows the use of particularly fine substrates while reducing the risk of breakage which can occur during these manipulations.
• the substrate may as well be monocrystalline as polycrystalline, or have a given negative or positive conductivity, be intrinsic or compensated, without the manufacturing process being modified. This makes it possible to use a very poor quality base material, therefore particularly inexpensive, without affecting the final yield of the cell;
• VHF process very high frequency plasma deposition process at a frequency substantially equal to 70 MHz
• VHF process very high frequency plasma deposition process at a frequency substantially equal to 70 MHz
• the deposition of the emitter and the back layer producing a surface field gives layers with a lower activation energy than that obtained using other methods. The behavior of these layers is then more favorable.
• the deposition of the doped microcrystalline layers makes it possible to obtain a better conductivity than using the methods of the prior art. This reduces the serial resistance of the cell, which increases its efficiency;
• the deposition of a microcrystalline silicon emitter reduces the absorption of the wavelengths belonging to the visible spectrum compared to a doped amorphous silicon emitter;

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• 1993
  • 1993-10-11 FR FR9312246A patent/FR2711276B1/fr not_active Expired - Fee Related
• 1994
  • 1994-09-27 JP JP7511140A patent/JPH08508368A/ja not_active Ceased
  • 1994-09-27 WO PCT/CH1994/000192 patent/WO1995010856A1/fr not_active Application Discontinuation
  • 1994-09-27 AU AU76506/94A patent/AU7650694A/en not_active Abandoned
  • 1994-09-27 US US08/446,628 patent/US5589008A/en not_active Expired - Lifetime
  • 1994-09-27 EP EP94926766A patent/EP0673549A1/de not_active Withdrawn

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