WO2012046306A1 - 光起電力装置およびその製造方法 - Google Patents
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- WO2012046306A1 WO2012046306A1 PCT/JP2010/067482 JP2010067482W WO2012046306A1 WO 2012046306 A1 WO2012046306 A1 WO 2012046306A1 JP 2010067482 W JP2010067482 W JP 2010067482W WO 2012046306 A1 WO2012046306 A1 WO 2012046306A1
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Classifications
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- 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
- H01L31/0232—Optical elements or arrangements associated with the device
- H01L31/02327—Optical elements or arrangements associated with the device the optical elements being integrated or being directly associated to the device, e.g. back reflectors
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- 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
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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- 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
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- 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 potential barriers
- H01L31/068—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 potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
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- 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
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
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- 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
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- 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
- Y02E10/547—Monocrystalline silicon PV cells
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a photovoltaic device and a manufacturing method thereof.
- the wavelength that has not been fully utilized before can be achieved by confining light in the photovoltaic device and suppressing the recombination speed of carriers on the front and back surfaces. It is important to realize structures and manufacturing methods that contribute to the generation of light in the region. Therefore, it is very important to improve the back surface structure of the substrate that plays the role.
- Patent Document 1 a film that suppresses the recombination rate is formed after the back electrode is printed and baked. In this case, especially during firing, the attachment and fixation of contaminants proceeds on the back surface of the substrate, and therefore it is extremely difficult to keep the carrier recombination rate on the back surface of the substrate low as intended. There is.
- an electrode paste is printed so as to cover almost the entire surface of the film that suppresses the recombination speed to form a back electrode that also functions as a light reflection function. This contact is partially made.
- the back electrode is made of, for example, a paste containing aluminum (Al), which is a typical material, the light reflectivity on the back surface cannot be increased, and sufficient photovoltaic power can be introduced into the photovoltaic device. There is a problem that the optical confinement effect cannot be obtained.
- the back electrode is made of, for example, a paste containing silver (Ag), which is a typical material
- a film that suppresses the recombination rate even in a region other than the original contact portion during the electrode firing process Is eroded by fire-through, and there is a problem that a sufficient effect of suppressing the recombination rate of carriers cannot be obtained.
- connection electrode on the cell side is formed by fire-through using a metal paste containing silver. By using fire-through, both electrical connection and physical adhesive strength can be obtained between the silicon substrate and the electrode.
- the open-circuit voltage (Voc) and the photoelectric conversion efficiency may be reduced by electrically connecting the back surface silver electrode and the silicon crystal of the silicon substrate in the back surface structure of the silicon solar cell.
- the present invention has been made in view of the above, and an object of the present invention is to obtain a photovoltaic device having a low recombination speed and a high back surface reflectance and excellent photoelectric conversion efficiency and a method for manufacturing the photovoltaic device.
- a photovoltaic device includes a first conductivity type semiconductor substrate having an impurity diffusion layer in which a second conductivity type impurity element is diffused on one side.
- An aluminum-based electrode connected to the other surface side of the semiconductor substrate, and a material comprising silver, provided on the other surface side of the semiconductor substrate in a region between the openings, and at least a part of the back surface insulating film.
- the sum of the area of the system electrode and the area of the peripheral region obtained by extending the pattern of the silver-based electrode outward in the plane of the semiconductor substrate by the diffusion length of carriers in the semiconductor substrate is the other surface of the semiconductor substrate. It is characterized by being 10% or less of the area on the side.
- FIG. 1-1 is a cross-sectional view of relevant parts for explaining the cross-sectional structure of the solar battery cell according to the first embodiment of the present invention.
- FIG. 1-2 is a top view of the solar battery cell according to the first embodiment of the present invention viewed from the light receiving surface side.
- FIG. 1-3 is a bottom view of the solar battery cell according to Embodiment 1 of the present invention as viewed from the back surface side.
- FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures.
- FIG. 3 is a characteristic diagram showing the relationship between the area ratio of the back electrode and the open circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the first embodiment.
- FIGS. 5-1 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-2 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-3 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-4 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-5 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-8 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-9 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIG. FIG. 5-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
- FIGS. FIGS. 5-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1
- FIG. 6-1 is a plan view showing an example of a printed region of the back surface aluminum electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention.
- FIG. 6-2 is a plan view showing an example of a printing region of the back surface aluminum electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention.
- FIG. 7 is principal part sectional drawing for demonstrating the cross-section of the photovoltaic cell concerning Embodiment 2 of this invention.
- FIG. 8-1 is a cross-sectional view of relevant parts for explaining the cross-sectional structure of the solar battery cell according to the third embodiment of the present invention.
- FIG. 8-2 is a top view of the solar battery cell according to the third embodiment of the present invention viewed from the light receiving surface side.
- FIG. 8-3 is a bottom view of the solar battery cell according to the third embodiment of the present invention as viewed from the back surface side.
- FIG. 9 is a characteristic diagram showing open-circuit voltages of the solar battery cells of Sample D to Sample F.
- FIG. 10 is a diagram showing the electrode area ratio of the back surface silver electrode in the solar cells of Sample D to Sample F.
- FIG. 11: is a top view which shows typically the influence area
- FIG. 12 is a characteristic diagram showing an example of the relationship between the ratio of the low open-circuit voltage region on the back surface of the silicon substrate and the open-circuit voltage.
- FIG. FIGS. 1-1 to 1-3 are diagrams showing a configuration of a solar battery cell that is a photovoltaic device according to the present embodiment, and FIG. 1-1 is for explaining a cross-sectional structure of the solar battery cell.
- 1-2 is a top view of the solar cell viewed from the light receiving surface side
- FIG. 1-3 is a bottom view of the solar cell viewed from the side opposite to the light receiving surface (back side). is there.
- FIG. 1-1 is a cross-sectional view of an essential part taken along line AA in FIG. 1-2.
- the solar cell according to the present embodiment includes a solar cell substrate having a photoelectric conversion function and having a pn junction, An antireflection film 4 made of a silicon nitride film (SiN film) which is an insulating film formed on the light receiving surface side (surface) and prevents reflection of incident light on the light receiving surface, and a light receiving surface side of the semiconductor substrate 1 On the surface (front surface), the light receiving surface side electrode 5 that is the first electrode formed surrounded by the antireflection film 4 and the silicon nitride film (back surface) opposite to the light receiving surface of the semiconductor substrate 1 (back surface)
- the semiconductor substrate 1 includes a p-type polycrystalline silicon substrate 2 which is a first conductivity type layer, and an impurity diffusion layer (n-type impurity diffusion) which is a second conductivity type layer formed by phosphorous diffusion on the light receiving surface side of the semiconductor substrate 1.
- the layer) 3 constitutes a pn junction.
- the n-type impurity diffusion layer 3 has a surface sheet resistance of 30 to 100 ⁇ / ⁇ .
- the light-receiving surface side electrode 5 includes a grid electrode 6 and a bus electrode 7 of the solar battery cell, and is electrically connected to the n-type impurity diffusion layer 3.
- the grid electrode 6 is locally provided on the light receiving surface to collect electricity generated by the semiconductor substrate 1.
- the bus electrode 7 is provided substantially orthogonal to the grid electrode 6 in order to take out the electricity collected by the grid electrode 6.
- the back surface aluminum electrode 9 is embedded in the back surface insulating film 8 provided over the entire back surface of the semiconductor substrate 1. That is, the back insulating film 8 is provided with a substantially circular dot-shaped opening 8 a that reaches the back surface of the semiconductor substrate 1.
- a back surface aluminum electrode 9 made of an electrode material containing aluminum, glass or the like is provided so as to fill the opening 8a and to have an outer shape wider than the diameter of the opening 8a in the in-plane direction of the back surface insulating film 8. Yes.
- the back insulating film 8 is made of a silicon nitride film (SiN film), and is formed on almost the entire back surface of the semiconductor substrate 1 by a plasma CVD (Chemical Vapor Deposition) method.
- SiN film silicon nitride film formed by the plasma CVD method
- the back surface reflecting film 10 is provided on the back surface of the semiconductor substrate 1 so as to cover the back surface aluminum electrode 9 and the back surface insulating film 8.
- the back surface reflecting film 10 covering the back surface insulating film 8
- the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained. it can.
- the back surface reflecting film 10 is comprised by the silver (Ag) film
- the solar battery cell according to the present embodiment can obtain an excellent light confinement effect by including the back surface reflection film 10 formed of a silver sputtering film.
- the material of the back surface reflection film 10 for example, it is preferable to use a metal material having a reflectance of 90% or more, preferably 95% or more with respect to light having a wavelength near 1100 nm.
- a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 to realize a high generated current and improve output characteristics.
- a material for example, aluminum (Al) can be used in addition to silver (Ag).
- the fine back surface aluminum electrode 9 is formed on the back surface of the semiconductor substrate 1, and the back surface reflection film 10 is formed thereon.
- the back surface reflecting film 10 shown in FIG. 1C actually has fine unevenness due to the back surface aluminum electrode 9, the description of the fine unevenness is omitted in FIG. ing.
- an aluminum-silicon (Al—Si) alloy portion 11 is formed in a region on the back surface side of the semiconductor substrate 1 and in the vicinity of the region in contact with the back surface aluminum electrode 9 and its vicinity.
- a BSF (Back Surface Filed Layer) 12 which is a high-concentration diffusion layer having the same conductivity type as that of the p-type polycrystalline silicon substrate 2 surrounding the aluminum-silicon (Al—Si) alloy portion 11 is provided on the outer periphery thereof. Is formed.
- the solar cell configured as described above, when sunlight is irradiated onto the semiconductor substrate 1 from the light receiving surface side of the solar cell, holes and electrons are generated.
- the generated electrons move toward the n-type impurity diffusion layer 3 due to the electric field of the pn junction (the junction surface between the p-type polycrystalline silicon substrate 2 and the n-type impurity diffusion layer 3), and the holes are p-type polycrystalline silicon. It moves toward the substrate 2.
- the number of electrons in the n-type impurity diffusion layer 3 becomes excessive, and the number of holes in the p-type polycrystalline silicon substrate 2 becomes excessive.
- a photovoltaic force is generated.
- This photovoltaic power is generated in the direction of biasing the pn junction in the forward direction, the light receiving surface side electrode 5 connected to the n-type impurity diffusion layer 3 becomes a negative electrode, and the back surface aluminum electrode 9 connected to the p-type polycrystalline silicon substrate 2. Becomes a positive pole, and current flows in an external circuit (not shown).
- FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures.
- FIG. 2 shows the relationship between the wavelength of light incident on the sample and the reflectance.
- Each sample is produced by imitating a solar battery cell, and the basic structure other than the back surface structure is the same as that of the solar battery cell according to this embodiment.
- the details of the back surface structure of each sample are as follows.
- Example A An aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back surface of the semiconductor substrate (corresponding to a conventional general structure).
- Sample B A back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back insulating film (preceding) Technology (equivalent to Patent Document 2)).
- a back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is locally provided on the back surface of the semiconductor substrate. Further, a high reflection film made of a silver sputtering film is provided on the entire surface of the back insulating film (corresponding to the solar battery cell according to the present embodiment).
- the sample B corresponding to the prior art has a slight improvement in reflectance as compared with the sample A corresponding to the conventional general structure, but the effect of improving the reflectance is sufficient. It can not be said.
- Sample C corresponding to the solar battery cell according to the present embodiment has a higher reflectance than Sample A and Sample B, and a high reflectance between “silicon (semiconductor substrate) and back surface structure” is recognized. Thus, it can be seen that it is suitable for high efficiency based on the light confinement action on the back surface.
- FIG. 3 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the open-circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the present embodiment in the same manner as the sample C described above.
- FIG. 4 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the short-circuit current in the sample manufactured by imitating the solar battery cell according to the present embodiment in the same manner as the sample C described above. It is the characteristic view which showed the relationship with a density (Jsc).
- the open circuit voltage (Voc) increases as the area ratio of the aluminum (Al) paste electrode as the back electrode decreases, that is, as the area ratio of the highly reflective film according to the present embodiment increases.
- the short-circuit current density (Jsc) are both improved, and it is recognized that a good carrier recombination rate suppressing effect is obtained on the back surface of the semiconductor substrate.
- the solar cell according to the first embodiment configured as described above by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement
- SiN film silicon nitride film
- the back surface reflection film 10 made of a silver sputtering film is provided so as to cover the back surface insulating film 8, thereby making it more than a silver (Ag) film formed by a conventional printing method.
- High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
- the solar cell according to the first embodiment by having the structure of the back surface having both the low recombination speed and the high back surface reflectance, the long-wavelength sensitivity is excellent and the photoelectric conversion efficiency is improved.
- the obtained solar battery cell is realized.
- FIGS. 5-1 to 5-9 are cross-sectional views for explaining the manufacturing process of the solar battery cell according to the present embodiment.
- a p-type polycrystalline silicon substrate that is most frequently used for consumer solar cells is prepared (hereinafter referred to as a p-type polycrystalline silicon substrate 1a) (FIG. 5-1).
- a p-type polycrystalline silicon substrate 1a for example, a polycrystalline silicon substrate having an electrical resistance of about 0.5 to 3 ⁇ cm containing a group III element such as boron (B) is used.
- the p-type polycrystalline silicon substrate 1a is manufactured by slicing an ingot formed by cooling and solidifying molten silicon with a wire saw, damage at the time of slicing remains on the surface. Therefore, the p-type polycrystalline silicon substrate 1a is first removed by immersing the surface of the p-type polycrystalline silicon substrate 1a in an acid or a heated alkaline solution, for example, in an aqueous solution of sodium hydroxide so as to remove the damaged layer. Thus, the damaged region existing near the surface of the p-type polycrystalline silicon substrate 1a is removed.
- the thickness of the p-type polycrystalline silicon substrate 1a after the damage removal is, for example, 200 ⁇ m, and the dimension is, for example, 150 mm ⁇ 150 mm.
- fine irregularities may be formed as a texture structure on the surface of the p-type polycrystalline silicon substrate 1a on the light receiving surface side.
- this invention is invention concerning the back surface structure of a photovoltaic apparatus, it does not restrict
- an alkaline aqueous solution containing isopropyl alcohol, a method using acid etching mainly composed of a mixed solution of hydrofluoric acid and nitric acid, or a mask material partially provided with an opening is formed on the surface of the p-type polycrystalline silicon substrate 1a.
- RIE reactive gas etching
- this p-type polycrystalline silicon substrate 1a is put into a thermal diffusion furnace and heated in an atmosphere of phosphorus (P) which is an n-type impurity.
- phosphorus (P) is diffused on the surface of the p-type polycrystalline silicon substrate 1a to form an n-type impurity diffusion layer 3 to form a semiconductor pn junction (FIG. 5-2).
- the n-type impurity diffusion layer 3 is formed by heating the p-type polycrystalline silicon substrate 1a in a phosphorus oxychloride (POCl 3 ) gas atmosphere at a temperature of, for example, 800 ° C. to 850 ° C.
- the heat treatment is controlled so that the surface sheet resistance of the n-type impurity diffusion layer 3 is, for example, 30 to 80 ⁇ / ⁇ , preferably 40 to 60 ⁇ / ⁇ .
- a phosphor glass layer mainly composed of phosphorus oxide is formed on the surface immediately after the formation of the n-type impurity diffusion layer 3, it is removed using a hydrofluoric acid solution or the like.
- a silicon nitride film (SiN film) is formed as the antireflection film 4 on the light receiving surface side of the p-type polycrystalline silicon substrate 1a on which the n-type impurity diffusion layer 3 is formed in order to improve the photoelectric conversion efficiency (FIG. 5-3).
- a plasma CVD method is used, and a silicon nitride film is formed as the antireflection film 4 using a mixed gas of silane and ammonia.
- the film thickness and refractive index of the antireflection film 4 are set to values that most suppress light reflection. Note that two or more films having different refractive indexes may be laminated as the antireflection film 4. Further, a different film forming method such as a sputtering method may be used for forming the antireflection film 4. Further, a silicon oxide film may be formed as the antireflection film 4.
- the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is removed by diffusion of phosphorus (P).
- P phosphorus
- the semiconductor substrate 1 having a pn junction is obtained (FIG. 5-4).
- the removal of the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is performed using, for example, a single-sided etching apparatus.
- a method of using the antireflection film 4 as a mask material and immersing the entire p-type polycrystalline silicon substrate 1a in an etching solution may be used.
- an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide heated to room temperature to 95 ° C., preferably 50 ° C. to 70 ° C. is used.
- a mixed aqueous solution of nitric acid and hydrofluoric acid may be used as the etching solution.
- the silicon surface exposed on the back surface of the semiconductor substrate 1 is washed in order to keep the recombination rate low in film formation described later.
- the cleaning is performed using, for example, RCA cleaning or a 1% to 20% hydrofluoric acid aqueous solution.
- a back surface insulating film 8 made of a silicon nitride film (SiN film) is formed on the back surface side of the semiconductor substrate 1 (FIG. 5-5).
- a back insulating film 8 made of a silicon nitride film (SiN film) having a refractive index of 1.9 to 2.2 and a thickness of 60 nm to 300 nm is formed on the silicon surface exposed on the back side of the semiconductor substrate 1 by plasma CVD. Film.
- plasma CVD plasma CVD, the back surface insulating film 8 made of a silicon nitride film can be reliably formed on the back surface side of the semiconductor substrate 1.
- the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be suppressed, and silicon (Si) and silicon nitride film (SiN film) on the back surface of the semiconductor substrate 1 can be suppressed. ), A recombination velocity of 100 cm / sec or less is obtained. Thereby, it is possible to realize a sufficient back surface interface for high output.
- the refractive index of the back surface insulating film 8 deviates from 1.9 to 2.2, it is difficult to stabilize the deposition environment of the silicon nitride film (SiN film), and the film quality of the silicon nitride film (SiN film) deteriorates. As a result, the recombination rate at the interface with silicon (Si) also deteriorates.
- the thickness of the back insulating film 8 is smaller than 60 nm, the interface with silicon (Si) is not stable, and the carrier recombination rate is deteriorated.
- the thickness of the back insulating film 8 is larger than 300 nm, there is no functional inconvenience, but it takes time to form a film and increases costs, which is not preferable from the viewpoint of productivity.
- the back insulating film 8 may have a two-layer structure in which a silicon oxide film (silicon thermal oxide film: SiO 2 film) formed by thermal oxidation and a silicon nitride film (SiN film) are stacked, for example.
- the silicon oxide film (SiO 2 film) here is not a natural oxide film formed on the back side of the semiconductor substrate 1 during the process, but a silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation, for example. To do.
- SiO 2 film silicon oxide film
- the effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained more stably than the silicon nitride film (SiN film).
- the thickness of the silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation is preferably about 10 nm to 50 nm.
- the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is less than 10 nm, the interface with silicon (Si) is not stable, and the recombination rate of carriers deteriorates.
- the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is larger than 50 nm, there is no functional inconvenience, but the film formation takes time and the cost increases. It is not preferable from the viewpoint.
- the film formation process is performed at a high temperature in order to shorten the time, the quality of the crystalline silicon itself is lowered, leading to a reduction in lifetime.
- dot-shaped openings 8a having a predetermined interval are formed on a part or the entire surface of the back insulating film 8 (FIGS. 5-6).
- the opening 8a is formed by performing direct patterning, for example, by laser irradiation on the back surface insulating film 8.
- the cross-sectional area of the opening 8 a in the in-plane direction of the back insulating film 8 is increased, and the opening of the opening 8 a in the plane of the back insulating film 8. It is preferable to increase the density.
- the cross-sectional area of the opening 8a is small and the opening density of the opening 8a is low. Therefore, it is preferable that the shape and density of the opening 8a be kept to a minimum level necessary for realizing a good contact.
- the shape of the opening 8a has a diameter or width of 20 ⁇ m to 200 ⁇ m, and a substantially circular dot shape or a substantially rectangular shape with an interval between adjacent opening portions 8a of 0.5 mm to 2 mm. Is mentioned.
- a stripe shape having a width of 20 ⁇ m to 200 ⁇ m and a distance between adjacent openings 8a of 0.5 mm to 3 mm can be cited.
- dot-shaped openings 8 a are formed by laser irradiation on the back surface insulating film 8.
- the application shape, application amount, and the like of the back surface aluminum electrode material paste 9a can be changed according to various conditions such as the diffusion concentration of aluminum in the Al—Si alloy part 11 and the BSF 12 in the firing step described later.
- the light reflectance (back surface reflectance) by the back surface aluminum electrode 9 in the region where the back surface insulating film 8 (silicon nitride film) and the back surface aluminum electrode 9 are laminated on the back surface of the semiconductor substrate 1 is not sufficient.
- the area where the back surface aluminum electrode material paste 9a is printed is limited to the minimum necessary after balancing the formation conditions of the Al—Si alloy part 11 and the BSF 12 and the light confinement effect in the photovoltaic device. There is a need.
- FIGS. 6A and 6B are plan views showing examples of the printing region of the back surface aluminum electrode material paste 9a on the back surface insulating film 8.
- FIGS. FIG. 6A shows an example in which the opening 8a has a substantially circular dot shape
- FIG. 6B shows an example in which the opening 8a has a substantially rectangular shape.
- Overlap amount is, 1000 .mu.m 2 from 200 [mu] m 2 in sectional area from the end of the opening 8a, preferably it is desirable to control in the range of 400 [mu] m 2 of 1000 .mu.m 2.
- the aluminum (Al) -containing back surface aluminum electrode material paste 9a has a paste thickness of 20 ⁇ m. Therefore, in terms of the width of the overlap, 10 ⁇ m to 50 ⁇ m, preferably 20 ⁇ m from the end of the opening 8a. It corresponds to the range of 50 ⁇ m.
- the overlap width is less than 10 ⁇ m, the effect of preventing the peeling of the back surface insulating film 8 is not exhibited, but the supply of aluminum (Al) does not work well during firing, that is, when the alloy is formed, and the BSF structure is not formed well. Part occurs.
- the overlap width is larger than 50 ⁇ m, the area ratio occupied by the paste printing portion increases, that is, the area ratio of the high reflection film decreases, and the deviation from the intention of the present invention becomes large.
- the outer periphery of the opening 8a on the back insulating film 8 includes a ring-shaped overlap region 9b having a width of 20 ⁇ m.
- the opening 8a has a substantially rectangular shape as shown in FIG. 6B
- a frame-shaped overlap region 9b having a width of 20 ⁇ m is provided on the outer periphery of the opening 8a on the back surface insulating film 8
- the back surface aluminum electrode material paste 9a is applied on the back surface insulating film 8 in a limited manner by screen printing.
- the width w of the opening 8a is 100 ⁇ m
- a light receiving surface electrode material paste 5 a which is an electrode material of the light receiving surface side electrode 5 and contains silver (Ag), glass or the like is formed into the shape of the light receiving surface side electrode 5.
- the light-receiving surface electrode material paste 5a is, for example, a pattern of elongated grid electrodes 6 with a width of 80 ⁇ m to 150 ⁇ m and a spacing of 2 mm to 3 mm, and a strip shape with a width of 1 mm to 3 mm and a spacing of 5 mm to 10 mm.
- the pattern of the bus electrode 7 is printed.
- the shape of the light receiving surface side electrode 5 is not directly related to the present invention, it may be freely set while balancing between the electrode resistance and the printing light shielding rate.
- firing is performed at a peak temperature of 760 ° C. to 900 ° C. using, for example, an infrared furnace heater.
- the light receiving surface side electrode 5 and the back surface aluminum electrode 9 are formed, and the Al—Si alloy part 11 is formed in the region on the back surface side of the semiconductor substrate 1 and in contact with the back surface aluminum electrode 9 and its vicinity. Is done.
- a BSF layer 12 which is a p + region in which aluminum is diffused in a high concentration from the back surface aluminum electrode 9 is formed on the outer peripheral portion so as to surround the Al—Si alloy portion 11, and the BSF layer 12, the back surface aluminum electrode 9, Are electrically connected (Fig. 5-8).
- the recombination speed at the interface deteriorates at this connection point, but the BSF layer 12 can negate this effect. Further, the silver in the light receiving surface side electrode 5 penetrates the antireflection film 4, and the n-type impurity diffusion layer 3 and the light receiving surface side electrode 5 are electrically connected.
- the back surface insulating film 8 made of a silicon nitride film (SiN film). The adherence and fixation of contaminants do not proceed with respect to the back surface, and a good state is maintained without degrading the recombination speed.
- a highly reflective structure is formed on the back side of the semiconductor substrate 1. That is, a silver (Ag) film (silver sputtering film) is formed as a back surface reflecting film 10 on the entire back surface of the semiconductor substrate 1 by sputtering so as to cover the back surface aluminum electrode 9 and the back surface insulating film 8 (FIGS. 5-9). ).
- a silver (Ag) film silver sputtering film
- a dense back surface reflection film 10 can be formed, and the back surface reflection film 10 that realizes higher light reflection than a silver (Ag) film formed by a printing method is formed. can do.
- the back surface reflection film 10 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1. .
- the solar battery cell according to Embodiment 1 shown in FIGS. 1-1 to 1-3 is manufactured.
- the order of application of the paste as the electrode material may be switched between the light receiving surface side and the back surface side.
- the back surface aluminum electrode material paste 9a is applied and fired. Therefore, the region where the back surface aluminum electrode material paste 9a is not applied is protected by the back surface insulating film 8. Thereby, even in the heating by baking, adherence and fixation of the contaminant do not proceed to the back surface of the semiconductor substrate 1, and a good state is maintained without deteriorating the recombination speed, and the photoelectric conversion efficiency is improved.
- the back surface reflecting film 10 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8.
- the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 10 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained.
- high photoelectric conversion efficiency can be realized.
- the back surface reflecting film 10 is formed by a sputtering method.
- a dense back surface reflecting film 10 can be formed by forming the back surface reflecting film 10 by a sputtering film, not by a printing method using an electrode paste, and realizes higher light reflection than a film formed by the printing method.
- the back reflective film 10 can be formed, and an excellent light confinement effect can be obtained.
- the manufacturing method of the solar cell according to the first embodiment it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency.
- Solar cells with high efficiency can be manufactured.
- the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
- FIG. Embodiment 2 demonstrates the case where the back surface reflecting film 10 is comprised with metal foil as another form of the back surface reflecting film 10.
- FIG. 7 is a cross-sectional view of relevant parts for explaining the cross-sectional structure of the solar battery cell according to the present embodiment, and corresponds to FIG. 1-1.
- the difference between the solar battery cell according to the second embodiment and the solar battery cell according to the first embodiment is that the back surface reflection film is formed of an aluminum foil (aluminum foil) instead of a silver sputtering film. Since the structure of those other than this is the same as that of the photovoltaic cell concerning Embodiment 1, detailed description is abbreviate
- the back surface reflection film 22 made of aluminum foil is formed by the conductive adhesive 21 disposed on the back surface aluminum electrode 9 on the back surface of the semiconductor substrate 1.
- the back surface aluminum electrode 9 and the back surface insulating film 8 are covered and attached, and are electrically connected to the back surface aluminum electrode 9 through the conductive adhesive 21. Even in such a configuration, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1 as in the case of the first embodiment, and good light confinement can be achieved with an inexpensive configuration. An effect can be obtained.
- the back surface reflecting film 22 is comprised by the aluminum foil which is metal foil.
- the back surface reflection film 22 is not a film formed by a printing method using an electrode paste, but is made of a metal foil, so that higher light reflection than a metal film formed by a printing method can be realized. More light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, the solar battery cell according to the present embodiment can obtain an excellent light confinement effect as in the case of the first embodiment by including the back surface reflection film 22 configured by the aluminum foil that is a metal foil. it can.
- the material of the back surface reflection film 22 a metal material that can be processed into a foil can be used.
- the reflectance with respect to light having a wavelength near 1100 nm is 90% or more, preferably 95%. It is preferable to use the above metal materials.
- a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 to realize a high generated current and improve output characteristics.
- a material for example, silver (Ag) can be used in addition to aluminum (Al).
- the solar battery cell according to the present embodiment configured as described above has a conductive adhesive on the back surface aluminum electrode 9 after the steps described in Embodiment 1 with reference to FIGS. 5-1 to 5-8. 21 is applied, and the back surface reflective film 22 is formed by covering the back surface aluminum electrode 9 and the back surface insulating film 8 with the conductive adhesive 21.
- the back surface reflection film 22 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1.
- the solar cell according to the second embodiment configured as described above, by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement
- SiN film silicon nitride film
- the back surface reflection film 22 made of aluminum foil that is a metal foil is provided so as to cover the back surface insulating film 8, thereby making it more than a metal film formed by a conventional printing method.
- High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
- the solar cell according to the second embodiment by having the structure of the back surface having both the low recombination speed and the high back surface reflectivity, the long wavelength sensitivity is excellent, and the photoelectric conversion efficiency is improved.
- the obtained solar battery cell is realized.
- the back surface insulating film 8 having the opening 8a is formed on the back surface of the semiconductor substrate 1, and then the back surface aluminum electrode material paste 9a is applied and fired.
- the region where the back surface aluminum electrode material paste 9 a is not applied is protected by the back surface insulating film 8.
- the back surface reflection film 22 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8.
- the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 22 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained.
- high photoelectric conversion efficiency can be realized.
- the back surface reflecting film 22 is formed by attaching an aluminum foil, which is a metal foil, on the back surface aluminum electrode 9.
- a dense back surface reflection film 22 can be formed by forming the back surface reflection film 22 using an aluminum foil that is a metal foil as the back surface reflection film 22 instead of a printing method using an electrode paste.
- the back surface reflection film 22 that realizes light reflection higher than that of the formed film can be formed, and an excellent light confinement effect can be obtained.
- the method for manufacturing a solar battery cell according to the second embodiment it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency. Solar cells with high efficiency can be manufactured. Further, since the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
- the case where a p-type silicon substrate is used as the semiconductor substrate has been described.
- a reverse conductivity type solar cell in which a p-type diffusion layer is formed using an n-type silicon substrate.
- a polycrystalline silicon substrate is used as the semiconductor substrate, a single crystal silicon substrate may be used.
- the substrate thickness of the semiconductor substrate is 200 ⁇ m.
- a semiconductor substrate that can be self-held, for example, thinned to about 50 ⁇ m, can be used.
- the size of the semiconductor substrate is 150 mm ⁇ 150 mm, but the size of the semiconductor substrate is not limited to this.
- Embodiment 3 In Embodiment 3, in the solar cell of Embodiment 1 and Embodiment 2 mentioned above, the connection electrode for connecting the metal tab which connects between cells when modularizing a photovoltaic cell was provided. The back surface structure will be described.
- the suppression of the recombination rate on the back surface has recently become particularly important.
- the carrier diffusion length it is not uncommon for the carrier diffusion length to exceed the thickness of the silicon substrate. Accordingly, the surface recombination speed on the back surface of the silicon substrate greatly affects the characteristics of the solar battery cell.
- a metal paste containing silver is often used as a material for a connection electrode provided on the cell side.
- Fire-through means that during paste application and baking, silver and glass components contained in the paste interact with silicon and bite into the silicon crystal, resulting in electrical connection and physical bond strength between the silicon substrate and the electrode. Both will be obtained.
- This phenomenon occurs similarly for silicon compounds such as a silicon nitride film (SiN film).
- SiN film silicon nitride film
- the silver and glass components contained in the paste penetrate through the silicon nitride film (SiN film) in a manner that breaks through the silicon nitride film (SiN film).
- the electrode and the silicon crystal can be connected without doing so. For this reason, fire-through greatly contributes to simplification of the solar cell manufacturing process.
- the fire-through is also performed in the steps shown in FIGS. 5-7 to 5-8 in the first embodiment.
- the recombination rate is very high at the interface between the silver electrode and silicon.
- the formation of electrodes by this fire-through becomes a big problem.
- the open circuit voltage (Voc) may be significantly reduced even by a slight contact between the back surface silver electrode and the silicon substrate. That is, the open-circuit voltage (Voc) and the photoelectric conversion efficiency may be reduced by electrically connecting the back surface silver electrode and the silicon crystal of the silicon substrate in the back surface structure of the silicon solar cell.
- the back surface structure of the silicon solar cell it is preferable to avoid the influence of the electrical connection between the back surface silver electrode and the silicon substrate while ensuring the physical adhesive strength between the back surface silver electrode and the back surface side of the silicon substrate.
- FIGS. 8-1 to 8-3 are diagrams illustrating a configuration of a solar battery cell that is the photovoltaic device according to the third embodiment, and FIG. 8-1 is for explaining a cross-sectional structure of the solar battery cell.
- 8-2 is a top view of the solar cell viewed from the light receiving surface side
- FIG. 8-3 is a bottom view of the solar cell viewed from the side opposite to the light receiving surface (back side). is there.
- FIG. 8A is a cross-sectional view of the main part along the line BB in FIG. 8B.
- the solar cell according to the third embodiment is different from the solar cell according to the first embodiment in that a back surface silver electrode 31 mainly composed of silver (Ag) is provided on the back surface side of the semiconductor substrate 1. . That is, the solar cell according to the third embodiment includes a back surface aluminum electrode 9 mainly composed of aluminum (Al) and a back surface silver electrode 31 mainly composed of silver (Ag) as the back surface side electrode. On the back side. Since the structure of those other than this is the same as that of the photovoltaic cell concerning Embodiment 1, detailed description is abbreviate
- the back surface silver electrode 31 is connected with a metal tab for connecting cells when modularizing solar cells.
- two back surface silver electrodes 31 are provided in a region between adjacent back surface aluminum electrodes 9 on the back surface side of the semiconductor substrate 1 so as to extend in a direction substantially parallel to the extending direction of the bus electrode 7.
- the back surface silver electrode 31 protrudes from the surface of the back surface reflection film 10 and penetrates the back surface insulating film 8 and is at least partially physically and electrically connected to the back surface of the semiconductor substrate 1.
- the width of the back surface silver electrode 31 is, for example, the same size as that of the bus electrode 7.
- Silver paste is usually used as a connection electrode material for silicon solar cells, and for example, lead boron glass is added.
- This glass is frit-like, and is composed of, for example, lead (Pb), boron (B), silicon (Si), oxygen (O), and further mixed with zinc (Zn), cadmium (Cd), and the like.
- Pb lead
- B boron
- Si silicon
- O oxygen
- Zn zinc
- Cd cadmium
- the back surface silver electrode 31 is formed by applying and baking such a silver paste and performing fire-through.
- Such back surface silver electrode 31 is obtained by applying and drying silver paste, which is an electrode material paste, in the shape of back surface silver electrode 31 in the region on back surface insulating film 8 in the process of FIG. However, it can be produced by fire-through by firing in the step of FIG. 5-8. Except for this, the solar battery cell according to the third embodiment can be manufactured by carrying out the steps of FIGS. 5-1 to 5-9 in the same manner as in the first embodiment.
- silver paste which is an electrode material paste
- Example D width 100 ⁇ m ⁇ length 148 mm ⁇ 75 (2 mm interval)
- Sample E width 3.5 mm ⁇ length 148 mm ⁇ 2 pieces (75 mm interval)
- Sample F width 7.5 mm ⁇ length 10 mm ⁇ 7 locations ⁇ 2 rows (75 mm interval)
- Sample G No back Ag paste printing (reference: comparison object)
- FIG. 9 is a characteristic diagram showing the open circuit voltage (Voc) of the solar cells of Sample D to Sample F.
- FIG. 10 is a diagram showing the electrode area ratio of the back surface silver electrode 31 in the solar cells of Sample D to Sample F.
- the electrode area ratio is the ratio of the area of the back surface silver electrode 31 to the area of the back surface of the p-type polycrystalline silicon substrate 2.
- the area of the back surface silver electrode 31 uses the printing area of the silver paste at the time of forming the back surface silver electrode 31. From FIG. 9, it can be seen that among the above four types of samples, the open circuit voltage (Voc) of sample D is greatly inferior compared to the others. On the other hand, it can be seen from FIG.
- the structure of the solar battery cell according to the third embodiment is for obtaining high efficiency, and the fact that the diffusion length of the single crystal or polycrystalline silicon used is large is cited as a practical precondition.
- a diffusion length of at least 300 ⁇ m or more, preferably 500 ⁇ m or more is required.
- the diffusion length is 500 ⁇ m will be described as an example.
- the influence on the open circuit voltage (Voc) of the back surface silver electrode 31 is due to the recombination speed of the interface.
- the term “influenced” here means that the generated carriers diffuse to the interface and recombine faster than the bulk recombination of the semiconductor material itself of the solar cell substrate. Therefore, the range of influence is not infinite and is closely related to the distance that the generated carriers can diffuse, that is, the diffusion length.
- FIG. 11 is a plan view schematically showing an influence area by the back surface silver electrode 31.
- the back reflection film 10 is seen through.
- FIG. 11 is a plan view, hatching is added to make the drawing easy to see.
- the influence region by the back surface silver electrode 31 includes the pattern region of the back surface silver electrode 31 and the peripheral region 32.
- Peripheral region 32 is a portion of the region where back surface insulating film 8 is formed on the back surface of p-type polycrystalline silicon substrate 2.
- the area ratio of the affected area by the back surface silver electrode 31 in Sample E and Sample F is slightly over 5%.
- region by the back surface silver electrode 31 in the sample D exceeds 50%.
- the open circuit voltage (Voc) decreases when the area ratio of the affected region by the back surface silver electrode 31 to the area of the back surface of the p-type polycrystalline silicon substrate 2 is large.
- Voc open circuit voltage
- a region having a high open-circuit voltage (Voc) (high open-circuit voltage region), that is, a highly passivated region on the back surface of the p-type polycrystalline silicon substrate 2, and an open-circuit voltage ( Voc) is a low region (low open circuit voltage region), that is, when a region greatly influenced by the back surface silver electrode 31 is mixed on the back surface of the p-type polycrystalline silicon substrate 2, the entire open circuit voltage (Voc) is based on parallel connection. Can think.
- FIG. 12 is a characteristic diagram showing an example of the relationship between the ratio of the low open-circuit voltage region on the back surface of the silicon substrate and the open-circuit voltage (Voc).
- the voltage in the high open-circuit voltage region is temporarily fixed at 655 mV and the voltage in the low open-circuit voltage region is temporarily fixed at 580 mV, and the change in the overall open-circuit voltage (Voc) according to the ratio between the two is calculated.
- the open circuit voltage (Voc) is required to be at least 635 mV or more, preferably 640 mV or more.
- the upper limit of the area ratio of the low open-circuit voltage region is calculated to be 10% or less, preferably 8% or less at most, referring to FIG.
- the back surface silver electrode 31 has an area ratio of about 3% or more in order to ensure its adhesion, because the original main function is to directly connect to the metal tab during tab connection. .
- the thickness of the back surface insulating film 8 made of a silicon nitride film (SiN film) formed on the back surface of the p-type polycrystalline silicon substrate 2 in order to obtain a sufficient effect of suppressing the surface recombination rate on the back surface side, A film thickness of 60 nm or more is required.
- the thickness of the back surface insulating film 8 is 160 nm or more, the fire-through in forming the back surface silver electrode 31 is difficult to reach the back surface of the p-type polycrystalline silicon substrate 2.
- the thickness of the back surface insulating film 8 is 240 nm or more, the fire through does not reach the back surface of the p-type polycrystalline silicon substrate 2 at all.
- the necessity of the device of the present invention does not occur at a film thickness of 160 nm or more, even if it is 240 nm or more.
- the thick film thickness hinders productivity, and the upper limit of the thickness of the back surface insulating film 8 according to the present embodiment is set to be less than 160 nm and at most less than 240 nm.
- the solar cell according to the third embodiment configured as described above, by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement
- SiN film silicon nitride film
- the back surface reflecting film 10 made of a silver sputtering film so as to cover the back surface insulating film 8 it is more than the silver (Ag) film formed by the conventional printing method. High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
- the ratio of the area of the influence region by the back surface silver electrode 31 to the area of the back surface of the p-type polycrystalline silicon substrate 2 is 10% or less, preferably 8% or less.
- the solar cell according to the third embodiment has a back surface structure that has both a low recombination speed and a high back surface reflectance, is excellent in long wavelength sensitivity and open circuit voltage (Voc), and has a photoelectric conversion efficiency. Solar cells with high efficiency have been realized.
- the photovoltaic device according to the present invention is useful for realizing a highly efficient photovoltaic device with a low recombination speed and a high back surface reflectance.
- SYMBOLS 1 Semiconductor substrate 1a p-type polycrystalline silicon substrate 2 p-type polycrystalline silicon substrate 3 n-type impurity diffusion layer 4 Antireflection film 5 Light-receiving surface side electrode 5a Light-receiving surface electrode material paste 6 Grid electrode 7 Bus electrode 8 Back surface insulating film 8a Opening Part 9 Back surface aluminum electrode 9a Back surface aluminum electrode material paste 9b Overlapping region 10 Back surface reflection film 11 Aluminum-silicon (Al-Si) alloy part 12 BSF layer 21 Conductive adhesive 22 Back surface reflection film 31 Back surface silver electrode 32 Peripheral region
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Abstract
Description
図1-1~図1-3は、本実施の形態にかかる光起電力装置である太陽電池セルの構成を示す図であり、図1-1は、太陽電池セルの断面構造を説明するための要部断面図、図1-2は、受光面側から見た太陽電池セルの上面図、図1-3は、受光面と反対側(裏面側)から見た太陽電池セルの下面図である。図1-1は、図1-2の線分A-Aにおける要部断面図である。
半導体基板の裏面全面にわたってアルミニウム(Al)を含む電極ペーストから形成したアルミニウム(Al)ペースト電極を備える(従来の一般的な構造に相当)。
(試料B)
半導体基板の裏面全面にわたってシリコン窒化膜(SiN)からなる裏面絶縁膜を形成し、該裏面絶縁膜上の全面にアルミニウム(Al)を含む電極ペーストから形成したアルミニウム(Al)ペースト電極を備える(先行技術(特許文献2)に相当)。
(試料C)
半導体基板の裏面全面にわたってシリコン窒化膜(SiN)からなる裏面絶縁膜を形成し、且つアルミニウム(Al)を含む電極ペーストから形成したアルミニウム(Al)ペースト電極を半導体基板の裏面の局所的に有し、さらに該裏面絶縁膜上の全面に銀スパッタリング膜からなる高反射膜を備える(本実施の形態にかかる太陽電池セルに相当)。
Ion Etching)を用いた手法など、何れの手法を用いても差し支えない。
実施の形態2では、裏面反射膜10の他の形態として、裏面反射膜10を金属箔により構成する場合について説明する。図7は、本実施の形態にかかる太陽電池セルの断面構造を説明するための要部断面図であり、図1-1に対応する図である。実施の形態2にかかる太陽電池セルが実施の形態1にかかる太陽電池セルと異なる点は、裏面反射膜が銀スパッタリング膜ではなく、アルミニウム箔(アルミニウムホイル)により構成されている点である。これ以外の構成は、実施の形態1にかかる太陽電池セルと同様であるため、詳細な説明は省略する。
実施の形態3では、上述した実施の形態1および実施の形態2の太陽電池セルにおいて、太陽電池セルをモジュール化する際にセル間を接続する金属タブを接続するための接続用電極を備えた裏面構造について説明する。
(試料E):幅3.5mm×長さ148mm×2本(75mm間隔)
(試料F):幅7.5mm×長さ10mm×7個所×2列(75mm間隔)
(試料G):裏Agペースト印刷なし(参考:比較対象)
1a p型多結晶シリコン基板
2 p型多結晶シリコン基板
3 n型不純物拡散層
4 反射防止膜
5 受光面側電極
5a 受光面電極材料ペースト
6 グリッド電極
7 バス電極
8 裏面絶縁膜
8a 開口部
9 裏面アルミニウム電極
9a 裏面アルミニウム電極材料ペースト
9b オーバーラップ領域
10 裏面反射膜
11 アルミニウム-シリコン(Al-Si)合金部
12 BSF層
21 導電性接着剤
22 裏面反射膜
31 裏面銀電極
32 周辺領域
Claims (22)
- 一面側に第2導電型の不純物元素が拡散された不純物拡散層を有する第1導電型の半導体基板と、
前記不純物拡散層上に形成された反射防止膜と、
前記反射防止膜を貫通して前記不純物拡散層に電気的に接続する第1電極と、
前記半導体基板の他面側に達する複数の開口部を有して前記半導体基板の他面側に形成された裏面絶縁膜と、
前記半導体基板の他面側に形成された第2電極と、
気相成長法によって形成される金属膜からなり、または金属箔を含んで構成され、少なくとも前記裏面絶縁膜上を覆って形成された裏面反射膜と、
を備え、
前記第2電極は、アルミニウムを含む材料からなり前記半導体基板の他面側において少なくとも前記開口部に埋め込まれて前記半導体基板の他面側に接続するアルミニウム系電極と、銀を含む材料からなり前記半導体基板の他面側において前記開口部間の領域に設けられて少なくとも一部が前記裏面絶縁膜を貫通して前記半導体基板の他面側に電気的に接続するとともに前記裏面反射膜を介して前記アルミニウム系電極と電気的に接続する銀系電極とからなり、
前記半導体基板の面内における前記銀系電極の面積と、前記半導体基板内におけるキャリアの拡散長分だけ前記銀系電極のパターンを前記半導体基板の面内において外側に拡張した周辺領域の面積との和が、上記半導体基板の他面側の面積の10%以下であること、
を特徴とする光起電力装置。 - 前記銀系電極の面積と前記周辺領域との和が、上記半導体基板の他面側の面積の8%以下であること、
を特徴とする、請求項1に記載の光起電力装置。 - 前記半導体基板がシリコン基板であり、前記拡散長が500μm以上であること、
を特徴とする請求項1または2に記載の光起電力装置。 - 前記半導体基板がシリコン基板であり、前記拡散長が300μm以上であること、
を特徴とする請求項1または2に記載の光起電力装置。 - 前記裏面絶縁膜が、プラズマCVD法により形成されたシリコン窒化膜であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記裏面絶縁膜が、熱酸化により形成されたシリコン酸化膜とプラズマCVD法により形成されたシリコン窒化膜とが前記半導体基板の他面側から積層された積層膜であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記シリコン酸化膜は、厚さが10nm以上50nm以下であること、
を特徴とする請求項6に記載の光起電力装置。 - 前記シリコン窒化膜は、屈折率が1.9以上2.2以下であり、厚さが60nm以上240nm未満であること、
を特徴とする請求項5または6に記載の光起電力装置。 - 前記シリコン窒化膜は、屈折率が1.9以上2.2以下であり、厚さが60nm以上160nm未満であること、
を特徴とする請求項5または6に記載の光起電力装置。 - 前記開口部は、径または幅が20μm~200μmの大きさであり、隣接する前記開口部間の間隔が0.5mm~2mmの略円形のドット状または略矩形形状であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記開口部は、幅が20μm~200μmであり、隣接する前記開口部間の間隔が0.5mm~3mmのストライプ状であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記アルミニウム系電極は、前記開口部に埋め込まれるとともに前記裏面絶縁膜上にオーバーラップして形成されていることを特徴とする請求項10または11に記載の光起電力装置。
- 前記アルミニウム系電極は、前記開口部の端部から10μm~50μmの幅で前記裏面絶縁膜上にオーバーラップして形成されていること、
を特徴とする請求項12に記載の光起電力装置。 - 前記金属箔は、アルミニウム箔であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記金属箔は、導電性接着剤により前記アルミニウム系電極に着設されるとともに前記導電性接着剤を介して前記アルミニウム系電極に電気的に接続されていること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 前記気相成長法によって形成される金属膜は、金属のスパッタリング膜もしくは蒸着膜であること、
を特徴とする請求項1~4のいずれか1項に記載の光起電力装置。 - 第1導電型の半導体基板の一面側に、第2導電型の不純物元素が拡散された不純物拡散層を形成する第1工程と、
前記不純物拡散層上に反射防止膜を形成する第2工程と、
前記半導体基板の他面側に裏面絶縁膜を形成する第3工程と、
前記裏面絶縁膜の少なくとも一部に前記半導体基板の他面側に達する複数の開口部を形成する第4工程と、
前記反射防止膜上に第1電極材料を塗布する第5工程と、
少なくとも前記複数の開口部を埋めるようにアルミニウムを含む第1の第2電極材料を前記半導体基板の他面側に塗布する第6工程と、
銀を含む第2の第2電極材料を前記裏面絶縁膜上に塗布する第7工程と、
前記第1電極材料、前記第1の第2電極材料および前記第2の第2電極材料を焼成して、前記反射防止膜を貫通して前記不純物拡散層に電気的に接続する第1電極と、アルミニウムを含み前記半導体基板の他面側において少なくとも前記開口部に埋め込まれて前記半導体基板の他面側に電気的に接続するアルミニウム系電極および銀を含み前記半導体基板の他面側において前記開口部間の領域に設けられて少なくとも一部が前記裏面絶縁膜を貫通して前記半導体基板の他面側に電気的に接続する銀系電極により構成される第2電極と、を形成する第8工程と、
気相成長法によって形成される金属膜からなり、または金属箔を含んで構成された裏面反射膜を、前記アルミニウム系電極と前記銀系電極とを電気的に接続するように少なくとも前記裏面絶縁膜上を覆って形成する第9工程と、
を含み、
前記半導体基板の面内における前記第2の第2電極材料の塗布面積と、前記半導体基板内におけるキャリアの拡散長分だけ前記第2の第2電極材料の塗布パターンを前記半導体基板の面内において外側に拡張した周辺領域の面積との和を、上記半導体基板の他面側の面積の10%以下とすること、
を特徴とする光起電力装置の製造方法。 - 前記第3工程では、前記裏面絶縁膜としてプラズマCVD法によりシリコン窒化膜を形成すること、
を特徴とする請求項17に記載の光起電力装置の製造方法。 - 前記第3工程では、前記裏面絶縁膜として前記半導体基板の他面側に熱酸化によりシリコン酸化膜を形成し、さらに前記シリコン酸化膜上にプラズマCVD法によりシリコン窒化膜を形成すること、
を特徴とする請求項17に記載の光起電力装置の製造方法。 - 前記第6工程では、前記開口部を埋めるとともに前記開口部の端部から10μm~50μmの幅で前記裏面絶縁膜上にオーバーラップさせて前記第2電極材料を塗布すること、
を特徴とする請求項17に記載の光起電力装置の製造方法。 - 前記金属箔は、アルミニウム箔であること、
を特徴とする請求項17に記載の光起電力装置の製造方法。 - 前記気相成長法によって形成される金属膜は、金属のスパッタリング膜もしくは蒸着膜であること、
を特徴とする請求項17に記載の光起電力装置の製造方法。
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- 2010-10-05 US US13/813,865 patent/US20130133741A1/en not_active Abandoned
- 2010-10-05 DE DE112010005921T patent/DE112010005921T5/de not_active Ceased
- 2010-10-05 JP JP2012537513A patent/JP5496354B2/ja not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
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TWI415280B (zh) | 2013-11-11 |
CN103180964B (zh) | 2015-12-16 |
JP5496354B2 (ja) | 2014-05-21 |
US20130133741A1 (en) | 2013-05-30 |
DE112010005921T5 (de) | 2013-09-26 |
JPWO2012046306A1 (ja) | 2014-02-24 |
TW201216484A (en) | 2012-04-16 |
WO2012046306A9 (ja) | 2012-12-13 |
CN103180964A (zh) | 2013-06-26 |
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