Back contact type solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, and particularly provides a back contact type solar cell and a preparation method thereof. The back contact type solar cell comprises a silicon substrate, a backlight surface of the silicon substrate is provided with a P + doping layer, an N + doping layer, an N + + doping layer and an air switch region between the P + doping layer and the N + doping layer, the P + doping layer, the N + doping layer and the air switch region are arranged in a staggered mode, the backlight surface of the silicon substrate is further provided with an insulating film, and the insulating film covers the air switch region, the N + doping layer, part of the P + doping layer and part of the N + + doping layer. The uncovered parts of the P + doping layer and the N + + doping layer are provided with electrodes. The permanent insulating film is arranged for pattern transfer, the back electrode of the battery piece is formed at a time, meanwhile, a welding strip structure is reduced, the high-temperature manufacturing process flow is avoided, the production efficiency of the battery piece can be effectively improved, and the function effectiveness of the battery piece can be effectively ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back-contact solar cell sheet and a preparation method thereof. Background Art

[0002] Back-contact solar cells, or BC (Back Contact) cells, do not refer to a type of battery, but a battery technology platform. In order to reduce front shading, all battery electrodes are directly integrated on the back of the battery, and the positive and negative metal grid lines are arranged in a cross-shaped pattern on the back of the battery. As a technology platform, back-contact solar cells can be combined with other batteries. Combining with heterojunction cells (HJT cells) is HBC, and combining with tunneling oxide passivation cells (Topcon) is TBC, etc. Through combination, the photoelectric conversion efficiency of the corresponding battery can be effectively improved. Therefore, the optimization and improvement of the BC battery manufacturing process has positive social significance and economic value for the development of photovoltaic fields and solar cells.

[0003] The current manufacturing process of BC batteries is complicated, especially for the production of positive and negative metal grid lines and electrodes. If electroplating is used, it is necessary to first prepare a bottom electrode on the back of the battery cell, and then prepare a protective coating on the surface of the bottom electrode by electroplating. After that, the positive and negative metal grid lines are gradually manufactured through multiple steps. This is the current mainstream process for manufacturing BC battery grid lines.

[0004] However, the metal grid lines produced in this way are of poor quality, and the bonding strength between the grid lines and the battery cells is insufficient. At the same time, when using solder ribbons for connection, soldering is required, which generally requires relatively high temperatures, which may affect the temperature-sensitive parts inside the battery cells, resulting in reduced efficiency of the battery cells or partial failure. Summary of the invention

[0005] The present invention provides a back-contact solar cell and a preparation method thereof, which are used to solve the defects of the prior art such as complex process and poor product quality, and simplify the process while ensuring product quality.

[0006] In a first aspect, the present invention provides a back-contact solar cell sheet, comprising a silicon substrate, wherein the backlight surface of the silicon substrate is provided with staggered P+ doped layers, N+ doped layers, N++ doped layers and open areas between the P+ doped layers and the N+ doped layers, and the backlight surface of the silicon substrate is also provided with an insulating film, wherein the insulating film covers the open areas, the N+ doped layers, part of the P+ doped layers and part of the N++ doped layers, and the uncovered parts of the P+ doped layers and the N++ doped layers are both provided with electrodes; the electrodes are higher than the insulating film.

[0007] In the prior art, the mask used for pattern transfer is generally removed, while the insulating film in the present invention is finally left on the battery cell, which not only simplifies the steps, but also plays an insulating and protective (weather-resistant, reflective, water-blocking, etc.) role, and further limits the electrode to be higher than the insulating film, which can ensure the lead-out of the electrode and facilitate the positioning of the electrode in subsequent processes.

[0008] According to the back-contact solar cell provided by the present invention, the insulating film is a cured product of an insulating resin composition, and when the insulating film is a transparent insulating film, its transmittance is greater than 82% within the wavelength range of 400 nm to 1200 nm; when the insulating film is a non-transparent insulating film, its reflectivity is greater than 78% within the wavelength range of 400 nm to 1200 nm.

[0009] The insulating resin composition of the present invention comprises: 20-45 parts by weight of epoxy resin, 8-10 parts by weight of epoxy curing agent, 2-6 parts by weight of curing agent accelerator, and 0-120 parts by weight of filler, dye and / or pigment.

[0010] The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, biphenyl epoxy resin, novolac epoxy resin, epoxy resin containing naphthalene ring, alicyclic epoxy resin, and sulfur-containing epoxy resin; The epoxy curing agent includes one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, hydrogenated xylylene isocyanate trimer, phenolic resin curing agent, naphthol curing agent with phenolic resin structure, and phenolic curing agent containing triazine skeleton; The curing accelerator includes one or more of imidazole derivatives, pyridine compounds, imidazole quaternary ammonium salts, pyridine quaternary ammonium salts, and urea derivatives.

[0011] Preferably, the insulating resin composition further comprises: 30 to 65 parts by weight of an alkali-soluble resin, 15 to 40 parts by weight of a photosensitive monomer and 1 to 5 parts by weight of a photoinitiator.

[0012] According to the back-contact solar cell provided by the present invention, the width of the open area is 10-100 μm.

[0013] According to the back-contact solar cell provided by the present invention, the width of the electrode is 5-100 μm.

[0014] According to the back-contact solar cell provided by the present invention, the thickness of the P+ doping layer and the N+ doping layer are both 100-500 nm.

[0015] According to the back-contact solar cell provided by the present invention, the thickness of the N++ doped layer is 15-35 nm.

[0016] According to the back-contact solar cell provided by the present invention, the thickness of the insulating film is 5-15 μm.

[0017] According to the back-contact solar cell provided by the present invention, the electrode is 3-5 μm higher than the insulating film.

[0018] In the above scheme, the structural firmness of the battery cell is enhanced by controlling the thickness of the insulating film and each layer, and it can also play the role of insulation and protection (weather resistance, reflection, water blocking, etc.).

[0019] In order to protect the electrode coating from water corrosion, it is preferred to use a protective film to fully cover the protective circuit metal.

[0020] Specifically, in some embodiments of the present invention, a protective film is further provided on the outer surface of the insulating film, and the water vapor transmission rate of the protective film is ≤15 g / m 2 •day, volume resistivity ≥10 13 Ω•m; preferably, the thickness of the protective film is 25~35 μm.

[0021] The protective film of the present invention can adopt the formula of the insulating film, and can also be obtained through regular commercial channels to obtain a protective film that meets the above-mentioned water vapor permeability and volume resistivity.

[0022] When the insulating film formula is adopted, the raw material composition of the protective film includes: 20-45 parts by weight of epoxy resin, 8-10 parts by weight of epoxy curing agent, 2-6 parts by weight of curing agent accelerator, and 0-120 parts by weight of filler, dye and / or pigment.

[0023] The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, biphenyl epoxy resin, novolac epoxy resin, epoxy resin containing naphthalene ring, alicyclic epoxy resin, and sulfur-containing epoxy resin; The epoxy curing agent includes one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, hydrogenated xylylene isocyanate trimer, phenolic resin curing agent, naphthol curing agent with phenolic resin structure, and phenolic curing agent containing triazine skeleton; The curing accelerator includes one or more of imidazole derivatives, pyridine compounds, imidazole quaternary ammonium salts, pyridine quaternary ammonium salts, and urea derivatives.

[0024] According to the back-contact solar cell provided by the present invention, the light-facing surface (also referred to as the front surface) of the silicon substrate is provided with a velvet structure and an anti-reflection layer to increase light capture and reduce reflection. The velvet structure may be a pyramid velvet structure.

[0025] Preferably, a front passivation layer is further provided between the suede structure and the anti-reflection layer.

[0026] Further preferably, the anti-reflection layer is selected from one or more of silicon dioxide, aluminum oxide, and silicon nitride. The front passivation layer is selected from one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, and silicon carbide, and the thickness of the front passivation layer is preferably 80-200 nm.

[0027] In a second aspect, the present invention provides a method for preparing the above-mentioned back-contact solar cell.

[0028] The preparation method provided by the present invention comprises the step of providing an insulating film on the backlight surface of a silicon substrate, wherein the step of providing the insulating film adopts one of the following two methods: Method 1: Use film lamination to apply the photosensitive insulating film to the back of the cell, and then form an electrode pattern through exposure and development; The remaining photosensitive insulating film portion after the above treatment is subjected to secondary curing at 130-150° C. for 5-15 minutes to fix the pattern.

[0029] Method 2: Printing the insulating resin composition on the back of the battery cell by screen printing to form an insulating resin composition film layer; The insulating resin composition film layer is thermally cured at 130-150° C. for 5-15 minutes to fix the pattern.

[0030] Specifically, when the insulating resin composition is a photosensitive resin composition, method one can be used, i.e. transferring the pattern by laminating, exposing and developing, and then thermally curing and shaping; method two can also be used, i.e. thermally curing and photocuring after screen printing.

[0031] When the insulating resin composition is a non-photosensitive resin composition, the second method is used, that is, the pattern is transferred by screen printing and then thermally cured to fix the shape.

[0032] The preparation of the insulating resin composition includes: according to the formula, the components are mixed evenly in proportion, a certain amount of butanone or other solvents that can evenly disperse the components are added, and then stirred until they are evenly dispersed to prepare an insulating resin composition glue with a solid content of 45-75%.

[0033] In method 1, a photosensitive insulating film needs to be prepared in advance before film lamination, and the preparation steps include: The insulating resin composition glue is evenly coated on the surface of the support film, and pre-baked at 70-85°C for 5-15 minutes to form an insulating resin composition film layer with a thickness of 10-15 μm; then, a release protective film is attached to the surface to obtain a photosensitive resin composition film with double-sided protection, which is placed in a freezer for storage and taken out for thawing when used, and the support film and the release protective film are peeled off to obtain the photosensitive insulating film.

[0034] After the photosensitive insulating film is obtained, a vacuum laminating machine, a roller laminating machine or a fast laminating machine may be used for laminating.

[0035] According to the method for preparing a back-contact solar cell provided by the present invention, after providing an insulating film,

[0036] Grooving the exposed electrode sites, providing an N++ doping layer at the grooves, and performing HF activation treatment; Electroless metal plating is performed on the N++ doped layer by chemical deposition; After the metal layer is plated by chemical deposition, the coating thickness is thickened by electroplating to ensure that the coating reaches the required level.

[0037] In some embodiments of the present invention, chemical metal plating is performed on the N++ doped layer by chemical deposition, including: The cell after HF activation treatment is further subjected to catalytic activation treatment to form activation sites; Chemical deposition is used to chemically plate metal on the exposed electrode sites and the N++ doped layer. Metals such as Ni, Cu, and Ag can be chemically plated. 0.5~1.5 μm of metal is chemically plated.

[0038] In some embodiments of the present invention, the thickness of the coating is increased by electroplating to ensure that the coating reaches the required thickness, including: Electrodes with 0.5~1.5μm metal deposited by chemical deposition already have good conductivity and can be further electroplated to quickly attach to electrodes of required thickness, generally 5~20μm.

[0039] The present invention provides a back-contact solar cell and a method for preparing the same. A permanent insulating film is provided for pattern transfer, and the back electrode of the cell is formed in one step. Meanwhile, the solder strip structure is reduced, and a high-temperature process flow is avoided, thereby effectively improving the production efficiency of the cell and ensuring the functional effectiveness of the cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 This is one of the embodiments of the back-contact solar cell provided by the present invention.

[0042] Figure 2 This is the second embodiment of the back-contact solar cell provided by the present invention.

[0043] 1-anti-reflection layer, 2-front passivation layer, 3-silicon substrate, 4-P+ doped layer, 5-insulating film, 6-protective film, 7-electrode, 8-N++ doped layer, 9-back passivation layer, 10-N+ doped layer. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0046] In a first aspect, the present invention provides a back-contact solar cell sheet, comprising a silicon substrate, wherein the backlight surface of the silicon substrate is provided with staggered P+ doped layers, N+ doped layers, N++ doped layers and open areas between the P+ doped layers and the N+ doped layers, and the backlight surface of the silicon substrate is also provided with an insulating film, wherein the insulating film covers the open areas, the N+ doped layers, part of the P+ doped layers and part of the N++ doped layers, and the uncovered parts of the P+ doped layers and the N++ doped layers are both provided with electrodes; the electrodes are higher than the insulating film.

[0047] In the prior art, the mask used for pattern transfer is generally removed, but the insulating film in the present invention is finally left on the battery cell, which not only simplifies the steps, but also plays an insulating and protective (weather-resistant, light-reflective, water-blocking, etc.) role.

[0048] It should be noted that N+ doping and P+ doping are doping modes with slightly higher doping concentrations than N doping and P doping. In the field of solar cells, there are also N++ doping and P++ doping, which are doping with higher concentrations. N doping and P doping are common doping of substrate silicon wafers.

[0049] According to the back-contact solar cell provided by the present invention, the insulating film is a cured product of an insulating resin composition. The insulating film may be a transparent insulating film or a non-transparent insulating film, and typical non-transparent insulating films are white insulating films or black insulating films. When it is a white insulating film, the white insulating film can reflect light (visible, infrared, etc. can be reflected) so that it is reabsorbed by the cell, thereby improving the light utilization rate of the cell, and ultimately improving the efficiency of the module. When it is a black insulating film, the aesthetics of the module can be improved, which is more in line with the requirements of BIPV (building integrated photovoltaics) for the appearance of the module. The black insulating film of a specific black pigment can also reflect infrared so that it is reabsorbed by the cell, thereby improving the light utilization rate of the cell, ultimately improving the efficiency of the module, and can also reduce the phenomenon of heating of the module due to the absorption of infrared by other hierarchical structures in the module.

[0050] Specifically, when the insulating film is a transparent insulating film, its average transmittance within the wavelength range of 400 nm to 1200 nm is greater than 82%; when the insulating film is a non-transparent insulating film, its average reflectivity within the wavelength range of 400 nm to 1200 nm is greater than 78%.

[0051] The insulating resin composition of the present invention comprises: 20-45 parts by weight of epoxy resin, 8-10 parts by weight of epoxy curing agent, 2-6 parts by weight of curing agent accelerator, and 0-120 parts by weight of filler, dye and / or pigment.

[0052] The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, biphenyl epoxy resin, novolac epoxy resin, epoxy resin containing naphthalene ring, alicyclic epoxy resin, and sulfur-containing epoxy resin. Novolac epoxy resin and bisphenol A epoxy resin are preferred, and examples thereof include BNE-200 (bisphenol A novolac epoxy resin, epoxy equivalent 190-200 g / eq, softening point 60-68°C); SH series (SH-3000, SH-7500, etc., bisphenol A epoxy resin, epoxy equivalent 220-250 g / eq, Hunan Servi Technology Co., Ltd.).

[0053] The epoxy curing agent includes one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, hydrogenated xylylene isocyanate trimer, phenolic resin curing agent, naphthol curing agent with phenolic resin structure, and phenolic curing agent containing triazine skeleton.

[0054] The curing accelerator includes one or more of imidazole derivatives, pyridine compounds, imidazole quaternary ammonium salts, pyridine quaternary ammonium salts, and urea derivatives.

[0055] The fillers include commonly used fillers such as silicon dioxide, titanium dioxide, and zinc oxide. Among them, titanium dioxide can be used as a filler (a small amount of it is added to the insulating film, and the film is still transparent), and can also be used as a white pigment to make the insulating film appear white. A small amount of silicon dioxide is added to the insulating film, and the insulating film is still transparent, but if it is added more, the insulating film may also appear white. That is, in theory, fillers can be added to transparent insulating films, but in actual operation, fillers, dyes, pigments and other additives are not required.

[0056] It is understandable that when the insulating film is a transparent insulating film, the insulating resin composition contains no or a small amount of dyes and / or pigments, and when the insulating film is a non-transparent insulating film, the insulating resin composition contains certain dyes and / or pigments to make the insulating film present the expected color. For example, when it is a white insulating film, white pigments such as titanium dioxide, barium sulfate, and calcium carbonate can be added alone, or white pigments and blue colorants can be added, because blue colorants can reduce the yellowing of white films; when it is a black insulating film, direct light-fast dyes, direct diazo dyes, direct cross-linking dyes, perylene black, carbon black and other dyes and / or pigments can be added, and color pigments (such as red, yellow, and blue, red, green, and blue, etc.) that make the film appear black after compounding can also be added, or black pigments + other color pigments can be added.

[0057] In order to allow the insulating film formed by curing to be photolithographically processed, preferably, the resin composition further comprises: 30 to 65 parts by weight of an alkali-soluble resin, 15 to 40 parts by weight of a photosensitive monomer and 1 to 5 parts by weight of a photoinitiator.

[0058] The alkali-soluble resin refers to a carboxyl-containing methacrylic acid and / or acrylic acid-modified epoxy resin, including (meth) acrylic acid-modified (including methacrylic acid modification and / or acrylic acid modification) bisphenol A epoxy resin, (meth) acrylic acid-modified bisphenol F epoxy resin, (meth) acrylic acid-modified bisphenol AF oligomer epoxy resin, (meth) acrylic acid-modified phenolic epoxy resin or (meth) acrylic acid-modified cresol phenolic epoxy resin. Examples include DIC's UE-9090, Nippon Kayaku's CCR series, UXE series, ZAR series, ZFR series, etc. For example, ZFR1401H in the ZFR series (bisphenol F epoxy acrylic resin, Nippon Kayaku, solid acid value 100 mgKOH / g).

[0059] The photosensitive monomer includes an acrylic ester monomer with a refractive index of 1.45 to 1.58. The refractive index affects the subsequent reflection. Too low or too high will affect the reflectivity, and it needs to be controlled within the range of 1.45 to 1.58. Specifically, one or more of the following monomers can be selected: Monofunctional (meth)acrylates such as (ethoxy)phenol (meth)acrylate, ethoxy (propoxy)nonylphenol (meth)acrylate, ethoxy (propoxy)tetrahydrofurfuryl (meth)acrylate; trifunctional (meth)acrylates such as 1,6-hexanediol diacrylate, tricyclohexanedimethanol diacrylate, dioxanediol diacrylate, ethoxylated (propoxylated) bisphenol A di(meth)acrylate, polyethylene glycol diacrylate, ethoxy (propoxy) trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanuric acid triacrylate; dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, aliphatic polyurethane hexaacrylate).

[0060] The photoinitiator can be a conventional photoinitiator in the art. Preferably, when there is a requirement for whether the insulating film turns yellow, for example, if the white insulating film needs to consider whether it turns yellow, a non-yellowing photopolymerization initiator is used, such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2,4,6-trimethylbenzoyl phenylphosphonic acid ethyl ester, oxime ester photoinitiator, etc. Because some photoinitiators will produce yellowing fragments after absorbing light energy and cracking. On this basis, considering the effect of improving the photocuring performance of the insulating resin composition and improving the photosensitivity, the two types of photopolymerization initiators, acylphosphine oxide and oxime ester, are preferred.

[0061] In order to meet other performance requirements, additives may be appropriately added according to specific circumstances. That is, the insulating resin composition further includes 0 to 8 parts by weight of other additives. The other additives include one or more of ultraviolet absorbers, antioxidants, defoamers, leveling agents, etc.

[0062] Specifically, the ultraviolet absorber can be benzophenone and / or benzotriazole. The antioxidant can be selected from phenolic antioxidants, hindered amine antioxidants, etc. The defoamer can be one or more of an organosilicon defoamer, a polyether defoamer, and a paraffin defoamer. The leveling agent can be one or more of a modified polysiloxane leveling agent and a long-chain resin leveling agent.

[0063] The insulating resin composition provided by the present invention can form a battery cell electrode pattern by photolithography and / or screen printing, and then form electrodes by chemical deposition and electroplating, thereby simplifying the electrode manufacturing process and effectively improving the quality of the electrode and the bonding strength with the battery cell. At the same time, the process flow does not have a high-temperature treatment section, which can effectively protect the internal structure of the battery cell from the influence of high temperature, thereby effectively maintaining the functional utility of the battery cell.

[0064] According to the back-contact solar cell provided by the present invention, the width of the open area is 10-100 μm.

[0065] According to the back-contact solar cell provided by the present invention, the width of the electrode is 5-100 μm.

[0066] According to the back-contact solar cell provided by the present invention, the thickness of the P+ doped layer and the N+ doped layer are both 100-500 nm, the thickness of the N++ doped layer is 15-35 nm, the thickness of the insulating film is 5-15 μm, and the electrode is 3-5 μm higher than the insulating film.

[0067] The present invention controls the thickness of the insulating film and each layer so that the layers can play a synergistic role and strengthen the structural firmness of the battery sheet. In order to protect the electrode coating from water corrosion, it is preferred to use a protective film to fully cover the protective circuit metal.

[0068] Specifically, in some embodiments of the present invention, a protective film is further provided on the outer surface of the insulating film, and the water vapor transmission rate of the protective film is ≤15 g / m 2 •day, volume resistivity ≥10 13 Ω•m; preferably, the thickness of the protective film is 25~35 μm.

[0069] The protective film of the present invention can adopt the formula of the insulating film, and can also be obtained through regular commercial channels to obtain a protective film that meets the above-mentioned water vapor permeability and volume resistivity.

[0070] When the insulating film formula is used, the raw material composition of the protective film includes: 20-45 parts by weight of epoxy resin, 8-10 parts by weight of epoxy curing agent, 2-6 parts by weight of curing agent accelerator, and 0-120 parts by weight of filler, dye and / or pigment. The specific types of each component are the same as those in the insulating film formula, and will not be repeated here.

[0071] According to the back-contact solar cell provided by the present invention, the light-facing surface (also referred to as the front surface) of the silicon substrate is provided with a velvet structure and an anti-reflection layer to increase light capture and reduce reflection. The velvet structure may be a pyramid velvet structure.

[0072] Preferably, a front passivation layer is provided between the velvet structure and the anti-reflection layer. The passivation layer can significantly improve the photoelectric conversion efficiency of the battery and enhance the stability and durability of the battery. The passivation layer can be used on the light-facing side of the battery cell or on the backlight side of the battery cell.

[0073] Further preferably, the anti-reflection layer is selected from one or more of silicon dioxide, aluminum oxide, and silicon nitride. The front passivation layer is selected from one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, and silicon carbide, and the thickness of the front passivation layer is preferably 80-200 nm.

[0074] According to the back-contact solar cell provided by the present invention, the backlight surface of the silicon substrate is also provided with a tunneling oxide layer and a back passivation layer, the tunneling oxide layer is located at the innermost side of the backlight surface of the silicon substrate, and the back passivation layer is located between the P+ doped layer and the electrode, and between the N+ doped layer, the N++ doped layer and the electrode.

[0075] Preferably, the tunneling oxide layer is silicon oxide; the back passivation layer is selected from one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, and silicon carbide, and the thickness of the back passivation layer is 60-180 nm.

[0076] In a second aspect, the present invention provides a method for preparing the above-mentioned back-contact solar cell.

[0077] The preparation method provided by the present invention comprises the step of providing an insulating film on the backlight surface of a silicon substrate, wherein the step of providing the insulating film adopts one of the following two methods: Method 1: Use film lamination to apply the photosensitive insulating film to the back of the cell, and then form an electrode pattern through exposure and development; The remaining photosensitive insulating film portion after the above treatment is subjected to secondary curing at 130-150° C. for 5-15 minutes to fix the pattern.

[0078] Method 2: Printing the insulating resin composition on the back of the battery cell by screen printing to form an insulating resin composition film layer; The insulating resin composition film layer is thermally cured at 130-150° C. for 5-15 minutes to fix the pattern.

[0079] It should be noted that in method one, a window is opened in the photosensitive insulating film through exposure and development, and the shape of the window is consistent with the shape of the electrode, so it is called forming an electrode pattern.

[0080] Specifically, when the insulating resin composition is a photosensitive resin composition, method one can be used, i.e., transferring the pattern by film lamination, exposure and development, and then thermally curing and shaping; method two can also be used, i.e., screen printing, thermal curing and photocuring and shaping. When the insulating resin composition is a non-photosensitive resin composition, method two is used, i.e., screen printing, transferring the pattern, and then thermally curing and shaping. When the thickness of the insulating film is above 10 μm, method one is generally used; when the thickness of the insulating film is less than 10 μm, method two is generally used.

[0081] The preparation of the insulating resin composition includes: according to the formula, the components are mixed evenly in proportion, a certain amount of butanone or other solvents that can evenly disperse the components are added, and then stirred until they are evenly dispersed to prepare an insulating resin composition glue with a solid content of 45-75%.

[0082] In method 1, a photosensitive insulating film needs to be prepared in advance before film lamination, and the preparation steps include: The insulating resin composition glue is evenly coated on the surface of the support film (substrate layer), and pre-baked at 70-85°C for 5-15 minutes to form an insulating resin composition film layer with a thickness of 10-15 μm; then, a release protective film is attached to its surface to obtain a photosensitive resin composition film (photosensitive layer) with double-sided protection (i.e., a three-layer structure), which is placed in a freezer for storage until use, and taken out for thawing when used, and the support film and the release protective film are peeled off to obtain the photosensitive insulating film.

[0083] Specifically, when in use, you can first peel off the release protective film, laminate the substrate layer-photosensitive layer and the battery cell, then expose to light, tear off the substrate layer, develop, and heat-cure; or, first peel off the release protective film, laminate the substrate layer-photosensitive layer and the battery cell, tear off the substrate layer, then expose to light, develop, and heat-cure; or, first peel off the release protective film and the substrate layer, laminate the photosensitive layer and the battery cell, then expose to light, develop, and heat-cure.

[0084] After the photosensitive insulating film is obtained, a vacuum laminating machine, a roller laminating machine or a fast laminating machine may be used for laminating.

[0085] According to the method for preparing a back-contact solar cell provided by the present invention, after providing an insulating film,

[0086] Grooving the exposed electrode sites, providing an N++ doping layer at the grooves, and performing HF activation treatment; Electrolessly plating metal on the N++ doped layer by chemical deposition; After the metal layer is plated by chemical deposition, the coating thickness is thickened by electroplating to ensure that the coating reaches the required level.

[0087] In some embodiments of the present invention, chemical metal plating is performed at the groove by chemical deposition, including: The cell after HF activation treatment is further subjected to catalytic activation treatment to form activation sites; Chemical deposition is used to chemically plate metal on the exposed electrode sites and the N++ doped layer. Metals such as Ni, Cu, and Ag can be chemically plated. 0.5~1.5μm metal is chemically plated.

[0088] In some embodiments of the present invention, the thickness of the coating is increased by electroplating to ensure that the coating reaches the required thickness, including: Electrodes with 0.5-1.5 μm metal deposited by chemical deposition already have good conductivity and can be further electroplated to quickly attach to electrodes of required thickness, generally 5-20 μm.

[0089] According to the method for preparing a back-contact solar cell provided by the present invention, the silicon substrate, i.e., the intrinsic semiconductor material layer, is formed by a physical vapor deposition method. The intrinsic semiconductor material layer can be used as a highly efficient carrier collection layer, which helps to improve the photoelectric conversion efficiency of the battery.

[0090] Regarding the formation of carrier collection terminals: Minority carrier collection terminals: Minority carrier collection terminals use one or more of silicon, silicon-carbon compounds, and silicon-germanium compounds. When it is a crystalline structure, it uses doping or epitaxial growth; when it is an amorphous structure, it uses physical deposition. Majority carrier collection terminals: use physical deposition or epitaxial growth methods.

[0091] In some specific embodiments of the present invention, the method for preparing the back-contact solar cell comprises the following steps: (1) Preparation of insulating resin composition film: Preparation of insulating resin composition: According to the formula table, mix the components in proportion according to weight, add a certain amount of butanone or other solvent that can evenly disperse the components, and then stir until they are evenly dispersed to prepare an insulating resin composition glue with a solid content of 45~75%.

[0092] The insulating resin composition glue prepared above is evenly coated on the surface of a PET support film or other available support film by a coating machine, and pre-baked in an oven at 85-95°C for 5-20 minutes to form an insulating resin composition film layer with a thickness of 10-25 μm. Then, a polyethylene protective film or other available release protective film is attached to the surface to obtain a three-layer structure of a photosensitive resin composition film, which is placed in a freezer for storage.

[0093] (2) Electrode pattern transfer: Pattern transfer to form a cross electrode reserved pattern: 1) Filming, exposure and development of photosensitive resin composition film product: Take the above-prepared photosensitive resin composition film product out of the freezer and thaw it at room temperature for 1 hour. After peeling off the polyethylene protective film, use a vacuum laminating machine or a roller laminating machine or a fast pressing machine to laminat (vacuum laminating machine: pressure 3.5~4kgf, vacuum time 20~60s, pressure time 20~60s, temperature 65~100℃; roller laminating machine: pressure 4~4.5kgf, temperature 100~110℃) to attach the photosensitive resin composition film product to the battery cell to be etched and plated with electrodes. After film pasting, place it in a place for 0.25~1h, then use a high-pressure mercury lamp exposure machine, under film isolation, use ST8 / 21 for exposure, development (using (0.22~0.25 mol / L tetramethylammonium hydroxide), and 120℃ oven drying, and the electrode pattern is basically finalized. 2) Screen printing of non-photosensitive resin composition film: The insulating resin composition is transferred to the battery cell through a screen printing screen that matches the electrode pattern using a screen printing process, and a preliminary finalization is performed to prevent glue flow from causing failure in electrode pattern printing.

[0094] Thermal curing: Thermal curing at 130~150℃ for 5~15min to complete the pattern.

[0095] (3) Slotting at the electrode: The grooves may be formed by mechanical grooves (mechanical grooves may be formed before step (2)) or by chemical etching, and an N++ doped layer may be provided at the grooves, followed by HF activation treatment.

[0096] (4) Chemical metal plating: By chemical deposition, chemical metal plating is performed on the N++ doped layer, which can be Ni, Cu, or Ag, depending on the actual situation.

[0097] (5) Electroplating metal: After the metal layer is plated by chemical deposition, the coating has good conductivity and can be further thickened by electroplating to ensure that the coating reaches the required level.

[0098] (6) Insulation protective layer: In order to protect the coating from water corrosion, a layer of insulating film is used to fully cover the metal of the protective circuit. The insulating protective film layer is a thermally cured product of an organic resin composition, and the water vapor transmission rate is ≤15 g / m 2 •day, volume resistivity ≥10 13 Ω•m.

[0099] It should be noted that the above preparation method mainly introduces the setting of an insulating film on the backlight surface of a back-contact solar cell and the subsequent processes. The setting of the light-facing surface of the cell, such as the setting of a velvet structure and an anti-reflection layer, as well as the setting of a P+ doped layer, an N+ doped layer, and an N++ doped layer can be performed according to conventional methods known in the art, and will not be repeated here.

[0100] The present invention is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed by the present invention.

[0101] The raw materials used in the following examples and comparative examples are as follows: Epoxy resin (A)

[0102] A1: JER YX8034 (hydrogenated bisphenol A epoxy resin, epoxy equivalent 250~360g / eq, liquid at room temperature, Mitsubishi, Japan).

[0103] A2: BNE-200 (bisphenol A novolac epoxy resin, epoxy equivalent 190~200g / eq, softening point 60~68℃, Taiwan Changchun Chemical).

[0104] A3: SQCN7004 (o-cresol-formaldehyde epoxy resin, epoxy equivalent 195~205g / eq, softening point 60~68℃, Shengquan New Materials).

[0105] Epoxy curing agent (B)

[0106] B1: PF8011 (Shengquan Group, phenolic epoxy curing agent).

[0107] B2: TAKENATE 600 (Mitsubishi Chemical, Japan, hydrogenated xylylene isocyanate trimer).

[0108] Curing accelerator (C)

[0109] C1: 2-Methyl-4-ethylimidazole (Aladdin, an imidazole derivative).

[0110] C2: 1-Benzylpyridinium chloride (Xiens Biochemical Technology, pyridinium salt).

[0111] Fillers, dyes, pigments (D)

[0112] D1: KRONOS 2075 (Kronos, titanium dioxide).

[0113] D2: L0086 (BASF, perylene black pigment); D3: SC2050-MNU (Yadouma, silica).

[0114] Alkali soluble resin (E)

[0115] E1: UE-9090 (acrylic acid modified epoxy resin, DIC, solid acid value 72~80mgKOH / g).

[0116] E2: ZFR1401H (bisphenol F type epoxy acrylic resin, Nippon Kayaku, solid acid value 100mgKOH / g).

[0117] Photosensitive monomer (F)

[0118] F1: DPHA (Sartomer, dipentaerythritol hexaacrylate, refractive index: 1.487).

[0119] F2: SR833NS (Sartomer, tricyclo[5.2.1.02,6]decanedimethanol acrylate, refractive index: 1.506).

[0120] Photoinitiator (G)

[0121] G1: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Aladdin, acylphosphine oxide photoinitiator).

[0122] G2: TR-PBG-305 (Changzhou Qiangli, oxime ester photoinitiator).

[0123] G3: 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer (Aituo Chemical, triaryl imidazole dimer).

[0124] Example 1

[0125] This embodiment provides a back-contact solar cell having a structure as follows: Figure 1 As shown, it includes a silicon substrate 3, and the front surface of the silicon substrate 3 is provided with an anti-reflection layer 1 and a front passivation layer 2. The back surface of the silicon substrate 3 is provided with a P+ doped layer 4, an N+ doped layer 10, an N++ doped layer 8 arranged in an interdigitated shape, and an open area between the P+ doped layer 4 and the N+ doped layer 10. The back surface of the silicon substrate 3 is also provided with an insulating film 5, and the insulating film 5 covers the open area, the N+ doped layer 10, part of the P+ doped layer 4 and part of the N++ doped layer 8. The uncovered part of the P+ doped layer 4 is provided with an electrode 7, and the uncovered part of the N++ doped layer 8 is provided with an electrode 7. The back surface of the silicon substrate 3 is also provided with a back passivation layer 9, and the back passivation layer 9 is located between the P+ doped layer 4 and the electrode 7, and between the N+ doped layer 10, the N++ doped layer 8 and the electrode 7.

[0126] The thickness of the P+ doped layer 4 and the N+ doped layer 10 are both 100 nm, the thickness of the N++ doped layer 8 is 15 nm, the thickness of the insulating film 5 is 5 μm, and the electrode 7 is higher than the insulating film 5 by 3 μm.

[0127] The width of the open area is 20 μm; the width of the electrode 7 is 15 μm.

[0128] The insulating film 5 is a cured product of the insulating resin composition, and the insulating film 5 is a non-transparent insulating film, and its reflectivity is 81% within the wavelength range of 400nm to 1200nm. The formula of the insulating resin composition is shown in Table 1 below.

[0129] The steps for preparing the back-contact solar cell provided in this embodiment are as follows: (1) Preparation of insulating resin composition: According to the formula table, mix the components in proportion according to weight, add a certain amount of butanone or other solvent that can evenly disperse the components, and then stir thoroughly until the components are evenly dispersed to prepare an insulating resin composition glue solution with a solid content of 45%.

[0130] (2) Electrode pattern transfer: The insulating resin composition is transferred to the battery cell (a silicon substrate with a P+ doped layer, an N+ doped layer and an open area) by a screen printing process using a screen printing screen that matches the electrode pattern, and is initially shaped to prevent the electrode pattern printing from failing due to glue flow.

[0131] Thermal curing: Thermal curing at 130°C for 15 minutes to complete the pattern.

[0132] (3) Slotting at the electrode: Mechanical grooves are formed, an N++ doped layer is provided at the grooves, and HF activation treatment is performed.

[0133] (4) Chemical metal plating: By chemical deposition, metal Cu is chemically plated on the N++ doped layer with a thickness of 0.5 μm.

[0134] (5) Electroplating metal: After the metal layer is plated by chemical deposition, the coating has good conductivity and can be further thickened to 8μm by electroplating.

[0135] Example 2

[0136] This embodiment provides a back-contact solar cell having a structure as follows: Figure 2As shown, it includes a silicon substrate 3, and the front surface of the silicon substrate 3 is provided with an anti-reflection layer 1 and a front passivation layer 2. The back surface of the silicon substrate 3 is provided with a P+ doped layer 4, an N+ doped layer 10, an N++ doped layer 8 arranged in an interdigitated shape, and an open area between the P+ doped layer 4 and the N+ doped layer 10. The back surface of the silicon substrate 3 is also provided with an insulating film 5, and the insulating film 5 covers the open area, the N+ doped layer 10, part of the P+ doped layer 4 and part of the N++ doped layer 8. The uncovered part of the P+ doped layer 4 is provided with an electrode 7, and the uncovered part of the N++ doped layer 8 is provided with an electrode 7. The back surface of the silicon substrate 3 is also provided with a back passivation layer 9, and the back passivation layer 9 is located between the P+ doped layer 4 and the electrode 7, and between the N+ doped layer 10, the N++ doped layer 8 and the electrode 7.

[0137] A protective film 6 is also provided on the side of the insulating film 5 away from the silicon substrate 3 .

[0138] The thickness of the P+ doped layer 4 and the N+ doped layer 10 are both 100 nm, the thickness of the N++ doped layer 8 is 15 nm, the thickness of the insulating film is 5 μm, and the electrode is 3 μm higher than the insulating film.

[0139] The width of the open area is 20 μm; the width of the electrode is 15 μm.

[0140] The water vapor permeability of the protective film is 13.5g / m 2 •day, volume resistivity is 3.1*10 14 Ω•m, and its thickness is 25 μm. The raw material composition of the protective film is shown in Table 1 below.

[0141] The insulating film is a cured product of an insulating resin composition, and is a white insulating film, and its reflectivity is 81% within a wavelength range of 400 nm to 1200 nm. The formula of the insulating resin composition is shown in Table 1 below.

[0142] The steps for preparing the back-contact solar cell provided in this embodiment are as follows: (1) Preparation of insulating resin composition film: According to the formula table, the components are mixed evenly in proportion according to weight, a certain amount of butanone or other solvent that can evenly disperse the components is added, and then stirred thoroughly until the components are evenly dispersed to prepare an insulating resin composition glue solution with a solid content of 65%.

[0143] (2) Electrode pattern transfer: The insulating resin composition is transferred to the battery cell (a silicon substrate with a P+ doped layer, an N+ doped layer and an open area) by a screen printing process using a screen printing screen that matches the electrode pattern, and is initially shaped to prevent the electrode pattern printing from failing due to glue flow.

[0144] Thermal curing: Thermal curing at 130°C for 15 minutes to complete the pattern.

[0145] (3) Slotting at the electrode: Grooves are formed by etching, an N++ doped layer is disposed at the grooves, and then an HF activation treatment is performed.

[0146] (4) Chemical metal plating: By chemical deposition, metal Cu is chemically plated on the N++ doped layer with a thickness of 1.0 μm.

[0147] (5) Electroplating metal: After the metal layer is plated by chemical deposition, the coating has good conductivity and can be further thickened to 8μm by electroplating.

[0148] (6) Insulation protective layer: In order to protect the coating from water corrosion, a layer of insulating film is used to fully cover the metal of the protective circuit. The insulating protective film layer is a thermally cured product of an organic resin composition, and the water vapor transmission rate is ≤15 g / m 2 •day, volume resistivity ≥10 13 Ω•m.

[0149] Example 3

[0150] This embodiment provides a back-contact solar cell, which is different from Embodiment 2 in that the raw material composition and performance of the protective film are different, as shown in Table 1 below.

[0151] Example 4

[0152] This embodiment provides a back-contact solar cell, which is different from Embodiment 2 in that the raw material composition and performance of the protective film are different, as shown in Table 1 below.

[0153] Embodiment 5-14

[0154] This embodiment provides a back-contact solar cell, which is different from Embodiment 1 in that the raw material composition and performance of the insulating film are different, as shown in Table 1 and Table 2 below.

[0155] In Example 13, the pattern is transferred by film pasting, exposure, and development, and the specific operations are as follows: (1) Preparation of insulating resin composition film: According to the formula table, the components are mixed evenly in proportion according to weight, a certain amount of butanone or other solvent that can evenly disperse the components is added, and then stirred thoroughly until the components are evenly dispersed to prepare an insulating resin composition glue solution with a solid content of 65%.

[0156] The insulating resin composition glue prepared above was evenly coated on the surface of the PET support film by a coating machine, and pre-baked in an oven at 85°C for 10 minutes to form an insulating resin composition film layer with a thickness of 15 μm. Then, a polyethylene protective film was attached to the surface to obtain a three-layer structure of a photosensitive resin composition film, which was placed in a freezer for storage.

[0157] (2) Electrode pattern transfer: The photosensitive resin composition film product is laminated, exposed and developed to form a cross electrode reserved pattern: The prepared photosensitive resin composition film product is taken out of the freezer and thawed at room temperature for 1 hour. After peeling off the polyethylene protective film, a vacuum laminating machine (pressure 3.5~4kgf, vacuum time 20~60s, pressure time 20~60s, temperature 65~100℃, specific parameters are adjusted according to the actual situation) is used to attach the photosensitive resin composition film product to the battery cell to be etched and plated with electrodes. After laminating, place it for 0.5h, and then use a high-pressure mercury lamp exposure machine, under film isolation, use ST8 / 21 for exposure, development (using (0.22~0.25 mol / L tetramethylammonium hydroxide), and 120℃ oven drying, and the electrode pattern is basically finalized.

[0158] Thermal curing: Thermal curing at 150°C for 5 minutes to complete the pattern.

[0159] The other steps are the same as those in Example 1.

[0160] Comparative Example 1

[0161] This comparative example provides a back-contact solar cell, which is different from Example 1 in that it does not contain an insulating film. The specific preparation method is as follows: a mask layer is set on the back of the silicon sheet, a laser ablation area is reserved for laser grooving, an N++ doping layer is set at the grooving, a 0.5 μm thick seed layer is deposited on the N++ doping layer by a chemical deposition method, and then a DECA100 low-temperature electrode material is printed on the back of the cell by a screen printing method to form an ohmic contact with the silicon wafer. Finally, the positive and negative electrodes are sintered at 180°C.

[0162] Comparative Example 2

[0163] This comparative example provides a back-contact solar cell, which is different from Example 1 in that FT3638 is used as the insulating film. The specific preparation method is as follows: the electroplated copper dry film FT3638 commercially available from Foster Electronic Materials Co., Ltd. is operated in the same manner as Example 1, and after film lamination, exposure, development, chemical plating, and electroplating, a 3wt% NaOH solution is used to remove the film to obtain the corresponding solar cell.

[0164] The following performance tests were performed on the back-contact solar cells of the embodiment and the comparative example, and the test results are shown in Table 1 and Table 2 below: Photoelectric conversion efficiency: See GB / T34160-2017 for test methods.

[0165] Weather resistance of battery cells: The battery cells are placed in an environment with a temperature of 85°C and a humidity of 85% for 120 hours, packaged, and subjected to a power test. Power loss below 3% is indicated as √; power loss between 3% and 8% is indicated as ○; power loss greater than 8% is indicated as ×.

[0166] Electrode and cell bonding test: The cell substrate with electrode grid lines was subjected to a 3M tape pull-off test. Ten pull-off tests were performed on the same part of a single sample. No pull-off occurred, which was indicated by √; one pull-off occurred, which was indicated by ○; and two or more pull-offs occurred, which was indicated by ×.

[0167] Electrode weather resistance: The battery cell is placed in an environment with a temperature of 85°C and a humidity of 85% for 120 hours to test the bonding strength between the electrode and the battery cell. A single sample is subjected to 10 pull-off tests on the same part. If the number of pull-offs is less than or equal to 1, it is represented by √; if the number of pull-offs is 2-3 times, it is represented by ○; if the number of pull-offs exceeds 3 times, it is represented by ×.

[0168] Table 1

[0169] Table 2

[0170] It can be seen from the experimental results in Table 1 and Table 2 that the back-contact solar cell of the present invention leaves an insulating film of a specific composition on the cell, which not only simplifies the steps of preparing the cell, but also improves the photoelectric conversion efficiency of the assembly. At the same time, the structural firmness of the cell is enhanced by controlling the thickness of each layer, so that it has excellent bonding strength with the electrode, and can also play an insulating and protective (weather-resistant, light-reflective, water-blocking, etc.) role, thereby improving the weather resistance of the cell. Further, by providing a protective film on the back-contact solar cell, the weather resistance of the electrode can also be improved.

[0171] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0172] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "specific implementation methods", or "some specific implementation methods" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A back-contact solar cell, characterized in that: It comprises a silicon substrate, wherein the backlight surface of the silicon substrate is provided with staggered P+ doped layers, N+ doped layers, N++ doped layers and open areas between the P+ doped layers and the N+ doped layers, and the backlight surface of the silicon substrate is also provided with an insulating film, wherein the insulating film covers the open areas, the N+ doped layers, part of the P+ doped layers and part of the N++ doped layers, and the uncovered parts of the P+ doped layers and the N++ doped layers are both provided with electrodes; and the electrodes are higher than the insulating film.

2. The back-contact solar cell according to claim 1, characterized in that: The insulating film is a cured product of an insulating resin composition. When the insulating film is a transparent insulating film, its transmittance is greater than 82% within a wavelength range of 400 nm to 1200 nm; when the insulating film is a non-transparent insulating film, its reflectivity is greater than 78% within a wavelength range of 400 nm to 1200 nm; The insulating resin composition comprises: 20 to 45 parts by weight of epoxy resin, 8 to 10 parts by weight of epoxy curing agent, 2 to 6 parts by weight of curing agent accelerator, and 0 to 120 parts by weight of filler, dye and / or pigment; Preferably, the insulating resin composition further comprises: 30 to 65 parts by weight of an alkali-soluble resin, 15 to 40 parts by weight of a photosensitive monomer and 1 to 5 parts by weight of a photoinitiator.

3. The back-contact solar cell according to claim 1, characterized in that: The width of the open area is 10-100 μm; And / or, the width of the electrode is 5-100 μm; And / or, the thickness of the P+ doped layer and the N+ doped layer are both 100-500 nm; And / or, the thickness of the N++ doped layer is 15-35 nm; And / or, the thickness of the insulating film is 5-15 μm; And / or, the electrode is 3-5 μm higher than the insulating film.

4. The back-contact solar cell according to any one of claims 1 to 3, characterized in that: The outer surface of the insulating film is also provided with a protective film, the water vapor permeability of the protective film is ≤15 g / m2•day, and the volume resistivity is ≥1013Ω•m; preferably, the thickness of the protective film is 25~35 μm.

5. The back-contact solar cell according to claim 4, characterized in that: The raw material composition of the protective film includes: 20-45 parts by weight of epoxy resin, 8-10 parts by weight of epoxy curing agent, 2-6 parts by weight of curing agent accelerator, and 0-120 parts by weight of filler, dye and / or pigment.

6. The back-contact solar cell according to claim 2 or 5, characterized in that: The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, biphenyl epoxy resin, novolac epoxy resin, epoxy resin containing naphthalene ring, alicyclic epoxy resin, and sulfur-containing epoxy resin; The epoxy curing agent includes one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, hydrogenated xylylene isocyanate trimer, phenolic resin curing agent, naphthol curing agent with phenolic resin structure, and phenolic curing agent containing triazine skeleton; The curing accelerator includes one or more of imidazole derivatives, pyridine compounds, imidazole quaternary ammonium salts, pyridine quaternary ammonium salts, and urea derivatives.

7. The method for preparing a back-contact solar cell according to any one of claims 1 to 6, characterized in that: The step includes providing an insulating film on the backlight surface of the silicon substrate, wherein the step of providing the insulating film adopts one of the following two methods: Method 1: Use film lamination to apply the photosensitive insulating film to the back of the cell, and then form an electrode pattern through exposure and development; The remaining photosensitive insulating film portion after the above treatment is subjected to secondary curing, with heat curing at 130-150°C for 5-15 minutes to fix the pattern; Method 2: Printing the insulating resin composition on the back of the battery cell by screen printing to form an insulating resin composition film layer; The insulating resin composition film layer is thermally cured at 130-150° C. for 5-15 minutes to fix the pattern.

8. The method for preparing a back-contact solar cell according to claim 7, characterized in that: In method 1, the preparation of the photosensitive insulating film includes: The insulating resin composition including epoxy resin, epoxy curing agent, curing agent accelerator, alkali-soluble resin, photosensitive monomer and photoinitiator is prepared into an insulating resin composition glue liquid with a solid content of 45-75% by using a solvent, the obtained glue liquid is evenly coated on the surface of the support film, and pre-baked at 70-85° C. for 5-15 minutes to form an insulating resin composition film layer with a thickness of 10-15 μm; then, a release protective film is attached to the surface thereof to obtain a photosensitive resin composition film with double-sided protection, which is placed in a freezer for storage and taken out for thawing when used, and the support film and the release protective film are peeled off to obtain the photosensitive insulating film; The film laminating is performed by using a vacuum laminating machine, a roller laminating machine or a fast pressing machine.

9. The method for preparing a back-contact solar cell according to claim 7 or 8, characterized in that: After setting the insulating film, Grooving the exposed electrode sites, providing an N++ doping layer at the grooves, and performing HF activation treatment; Electrolessly plating metal on the N++ doped layer by chemical deposition; After the metal layer is plated by chemical deposition, the coating thickness is thickened by electroplating to ensure that the coating reaches the required level.

10. The method for preparing a back-contact solar cell according to claim 9, characterized in that: The chemically plated metal is selected from one or more of Ni, Cu, and Ag, and the thickness of the chemically plated metal is 0.5-1.5 μm.

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