Composite photo-sensitive adhesive for preparing solar cell, stripping liquid, solar cell and preparation method of solar cell

Abstract

The invention relates to the technical field of solar cells, in particular to a composite photo-sensitive adhesive for preparing a solar cell, a stripping liquid, the solar cell and a preparation method of the solar cell. The preparation method comprises the following steps: coating a yellow diaphragm with a composite photo-sensitive adhesive, and carrying out printing exposure; carrying out edge etching by using an ITO etching solution; cleaning with a stripping solution; developing and electroplating to form a copper grid line; the composite photo-sensitive adhesive is prepared from the following components in percentage by mass: 0.8 to 1.2 percent of sodium molybdate particles, 0.05 to 0.2 percent of polyvinylpyrrolidone and photo-sensitive adhesive; and / or the stripping liquid comprises sodium hydroxide with the mass concentration of 30 + / -5 g / L, ethylenediamine tetraacetic acid disodium salt with the mass percentage of 0.05-0.2% and water. According to the preparation method, the binding force of the electroplated grid line can be improved, the problems of grid line separation and grid breakage are solved, and the yield of the solar cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a composite photosensitive adhesive for preparing a solar cell, a stripping solution, a solar cell and a preparation method thereof. BACKGROUND

[0002] The solar cell (for example, a heterojunction cell) provided by the related technology can be prepared with a copper interconnection technology in addition to the method of preparing a grid line by printing silver paste.

[0003] The copper interconnection technology generally includes: first, depositing a copper seed layer on an ITO (TCO) conductive film by PVD sputtering for conduction (that is, preparing a seed layer for electroplating), then coating and printing on the seed layer, and then performing edge etching (that is, removing the seed layer at the edge of the solar cell piece, so as to ensure that the edge of the solar cell piece is not conductive during electroplating, so as to prevent the solar cell piece from being plated with copper, thereby solving the problem of short circuit caused by the conduction of the N-P surface) by using an edge etching process in order to prevent the side of the solar cell piece from being plated with copper, which causes the N-P surface to be directly conductively connected to form a short circuit, resulting in high leakage and loss of efficiency, then developing to realize pattern transfer, and then electroplating copper grid lines, and then plating a layer of protective tin on the electroplated copper grid lines by using a chemical tin plating method.

[0004] The edge etching process provided by the related technology generally includes: immersing the solar cell piece after coating and printing in an ITO etching solution to etch the blue film at the edge of the solar cell piece by using the ITO etching solution to expose the silicon layer.

[0005] However, the edge etching process provided by the related technology is prone to cause denaturation of the unexposed adhesive film on the solar cell piece, which makes it difficult to develop or develop insufficiently; and the ITO etching solution remains in the unexposed adhesive film, causing consumption of the developing solution and further reducing the developing effect, resulting in residual adhesive in the groove. The above reasons will cause the morphology of the pre-plating groove after development to be poor, which further adversely affects the contact between the copper seed layer and the electroplated copper, reduces the adhesion of the electroplated copper grid line, causes the grid line to separate and break, and reduces the yield of the prepared solar cell. SUMMARY

[0006] The application aims to provide a composite photosensitive glue, a stripping solution and a solar cell for preparing the solar cell and a preparation method thereof.

[0007] The application is implemented as follows: In a first aspect, the application provides a composite photosensitive glue for preparing a solar cell, comprising: a photosensitive glue, sodium molybdate particles and polyvinylpyrrolidone; wherein the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinylpyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue.

[0008] In an optional embodiment, the particle size of the sodium molybdate particles is 30-50 nm.

[0009] In a second aspect, the application provides a stripping solution for preparing a solar cell, comprising: sodium hydroxide, disodium EDTA and water; wherein the mass concentration of the sodium hydroxide is 30±5 g / L, the mass percentage of the disodium EDTA is 0.05-0.2%, and the rest is water.

[0010] In a third aspect, the application provides a preparation method of a solar cell, comprising: coating the composite photosensitive glue on a copper seed layer of a yellow film sheet and printing and exposing; performing edge etching by using a strong-acid ITO etching solution; cleaning by using the stripping solution; developing to form a pre-plating groove; forming a copper grid line in the pre-plating groove; wherein, the composite photosensitive glue comprises the photosensitive glue, the sodium molybdate particles and the polyvinylpyrrolidone; wherein the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinylpyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue; and / or, The stripping solution comprises sodium hydroxide, disodium ethylenediaminetetraacetate and water, wherein the mass concentration of sodium hydroxide is 30±5 g / L, the mass percentage of disodium ethylenediaminetetraacetate is 0.05-0.2%, and the rest is water.

[0011] In an optional embodiment, the particle size of the sodium molybdate particles is 30-50 nm.

[0012] In an optional embodiment, the temperature during the cleaning with the stripping solution is greater than or equal to 30℃.

[0013] In an optional embodiment, the temperature of the edge etching is 30-40℃.

[0014] In an optional embodiment, the step of cleaning with the stripping solution specifically comprises: cleaning under ultrasonic conditions.

[0015] In an optional embodiment, the frequency of the ultrasonic conditions is 40±5 kHz, the power is 100±5 W, and the stripping solution is circulated at a circulation flow rate of 100±5 LPM.

[0016] In a fourth aspect, the present application provides a solar cell prepared by the method for preparing a solar cell according to any one of the preceding embodiments.

[0017] The present application has the following advantages: The composite photosensitive adhesive provided by the embodiments of the present application adds sodium molybdate and polyvinylpyrrolidone, so that when the unexposed composite photosensitive adhesive contacts the ITO etching solution, a dense FeMoO4·nH2O composite passivation film is formed, the composite passivation film is used to block the ITO etching solution from attacking the unexposed adhesive film, that is, to block the ITO etching solution from contacting the unexposed photosensitive adhesive, thereby playing a role in protecting the adhesive film, so as to ensure reliable development in the subsequent process, and is beneficial to improving the morphology of the pre-plating groove after development.

[0018] The raw materials of the stripping solution provided by the embodiments of the present application include a strong base and disodium EDTA, and in an alkaline environment, the FeMoO4·nH2O composite passivation film will react to generate Fe(OH)3 and MoO4 2- , and the Fe(OH)3 will react with EDTA in an alkaline environment to generate a soluble [Fe(EDTA)] - complex, so as to promote reliable dissolution and stripping of the FeMoO4·nH2O composite passivation film, and further ensure the reliability of subsequent development, which is beneficial to improving the morphology of the pre-plating groove after development.

[0019] The preparation method of the solar cell provided in the embodiment of the present application contains sodium molybdate particles and polyvinylpyrrolidone in the coated composite photosensitive glue, and when subsequent edge etching is performed by using a strong-acid ITO etching solution, a dense FeMoO4·nH2O composite passivation film is formed to protect the unexposed photosensitive glue, so that the ITO etching solution cannot directly contact the unexposed photosensitive glue, and thus the denaturation problem of the unexposed photosensitive glue cannot be caused, and the development difficulty or insufficiency problem is improved; moreover, due to the protection of the composite passivation film, the problem of ITO etching solution remaining in the unexposed glue film to cause a large amount of consumption of the developing solution is also improved, so that the development effect is improved, and the problem of glue film remaining in the pre-plating groove is improved; after edge etching, cleaning is performed by using an alkaline stripping solution containing disodium EDTA, the FeMoO4·nH2O composite passivation film reacts to generate Fe(OH)3 and MoO4 2- , and the Fe(OH)3 reacts with EDTA in an alkaline environment to generate a soluble [Fe(EDTA)] - complex, so as to promote reliable dissolution and stripping of the FeMoO4·nH2O composite passivation film; in this way, the morphology of the pre-plating groove can be fully improved, the contact stability of the copper seed layer and the electroplated copper is improved, the adhesion of the electroplated grid line is improved, the problems of grid line separation and grid breakage are improved, and the yield of the solar cell is improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 The groove photos of the cell pieces after development in the embodiments 1-2 of the present application; Figure 2 The groove photos of the cell pieces after development in the comparative example 1 of the present application; Figure 3 The grid line separation photos of the cell pieces in the comparative example 1 of the present application; Figure 4 The grid line separation and residual copper type grid breakage ratio column charts of the cell pieces in the embodiments 1-2 and the comparative example 1 of the present application; Figure 5 The stripping time fold line graphs of the embodiments 1-1~1-6, 2-1~2-6, and the comparative examples 2-1~2-6 in the present application. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] The related technologies provide methods for fabricating solar cells, including: 1. Cleaning and texturing: Acid and alkali solutions are used to etch the surface of the original silicon wafer to form a pyramidal textured surface, improving surface utilization.

[0024] 2. PECVD, vapor deposition of an amorphous silicon layer onto a textured surface to prepare the substrate for forming a PN junction.

[0025] 3. PVD / RPD: After the PN junction is formed, a conductive transparent film is formed on its surface.

[0026] 4. PVD-Cu: Due to the poor conductivity of TCO, a high-conductivity copper seed layer is pretreated on the surface of TCO to improve the poor adhesion between electroplated copper and TCO.

[0027] 5. Coating: Apply a layer of negative photosensitive adhesive (as an electroplating mask) to the front and back of the yellow film (the semi-finished battery cell after copper seed layer deposition).

[0028] 6. Printing exposure: Use a light source with a wavelength greater than 400nm to expose the non-grid line parts to induce a cross-linking reaction in the mask, causing it to denature and become less susceptible to corrosion by weak alkaline solutions.

[0029] 7. Edge etching (edge ​​etching): The edges and corners of the yellow film are etched using ITO etching solution to prevent copper metal from being electroplated onto the edges and corners of the yellow film, which would cause a path between the front and back sides. Specifically, the printed cell is immersed in ITO etching solution at 35°C for 150 seconds until the edges of the cell are completely etched down to the silicon layer. After removal, it is rinsed twice with overflow pure water and dried at low temperature.

[0030] 8. Development: Use Na2CO3 solution to rinse the mask, so that the unexposed reaction parts of the mask are cleaned to form pre-plated grooves.

[0031] 9. Electroplating, utilizing the principle of a galvanic cell, causes the Cu in the electroplating solution to... 2+ The electrons migrate to the surface of the PVD copper seed layer with the electric field, capture electrons, and deposit to fill the pre-plated grooves formed after development.

[0032] 10. Etching back: Dissolve the mask adhesive and edge-sealing adhesive with strong alkaline solution, and use strong oxidizing acid to etch the PVD-copper seed layer until the ITO layer is exposed.

[0033] 11. Light injection, using infrared light to repair Si-H bonds, saturate internal defects of the heterojunction cell, and high-temperature annealing to release internal stress of the silicon wafer and plating layer.

[0034] 12. Tin plating, using chemical solution to replace Cu element on the surface of the copper grid lines and form a tin layer on the surface of the copper grid lines to protect the copper grid lines from being oxidized by air.

[0035] The inventors found that since the ITO etching solution used in the edge cutting process is a strong oxidizing strong acid solution, it not only etches the edges of the cell, but also attacks the photosensitive adhesive film on the surface of the cell. That is, the unexposed adhesive film in the pattern area has weak resistance to cross-linking and curing, and the ITO etching solution entering the unexposed adhesive film area will cause the adhesive film to denature. At the same time, the residual ITO etching solution in the unexposed adhesive film area is a strong acid liquid, which will react with the alkaline liquid used for development and further weaken the development effect. The direct result is that the development is insufficient, and there is residual adhesive at the bottom of the pre-plating groove after development, resulting in residual adhesive and gaps between the copper seed layer and the electroplated copper, that is, poor contact between the copper seed layer and the electroplated copper, ultimately resulting in reduced adhesion of the electroplated copper grid lines, easy grid line mesh shedding and residual copper type grid breakage, affecting the yield of the cell.

[0036] To improve the above problems, the present disclosure proposes a synergistic optimization scheme of acid etching passivation and alkali solution de-passivation. First, the adhesive film is passivated under acidic etching conditions to prevent the ITO etching solution from attacking the photosensitive adhesive film. After etching is completed, the adhesive film is de-passivated by an alkaline solution to dissolve and strip the passivation film, and development is successfully performed.

[0037] Specifically, the present disclosure provides a composite photosensitive adhesive for preparing a solar cell, comprising: a photosensitive adhesive, sodium molybdate particles, and polyvinylpyrrolidone; wherein the mass percentage of sodium molybdate particles is 0.8-1.2% (for example: 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, etc., which are not specifically limited here), the mass percentage of polyvinylpyrrolidone is 0.05-0.2% (for example: 0.05%, 0.1%, 0.15%, 0.20%, etc., which are not specifically limited here), and the balance is the photosensitive adhesive.

[0038] The addition of sodium molybdate and polyvinylpyrrolidone in the composite photosensitive adhesive facilitates the formation of a dense FeMoO4·nH2O composite passivation film when the unexposed composite photosensitive adhesive comes into contact with the ITO etching solution, so as to block the ITO etching solution from attacking the unexposed adhesive film, that is, to block the ITO etching solution from contacting the unexposed photosensitive adhesive, thereby protecting the adhesive film and ensuring reliable development, which is beneficial to improving the morphology problem of the pre-plating groove after development.

[0039] Optionally, the particle size of the sodium molybdate particles is 30-50 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc., which is not limited herein. The addition of nanoscale sodium molybdate particles is conducive to ensuring the compactness of the composite passivation film formed, thereby providing more reliable protection for the unexposed photosensitive glue.

[0040] Optionally, the photosensitive glue refers to a negative photosensitive glue.

[0041] The present disclosure also provides a stripping solution used in cooperation with the composite photosensitive glue, comprising: sodium hydroxide, disodium ethylenediaminetetraacetate, and water; wherein the mass concentration of sodium hydroxide is 30±5 g / L (for example, 25 g / L, 28 g / L, 30 g / L, 32 g / L, 35 g / L, etc., which is not limited herein), the mass percentage of disodium ethylenediaminetetraacetate is 0.05-0.2% (for example, 0.05%, 0.1%, 0.15%, 0.2%, etc., which is not limited herein), and the balance is water.

[0042] The raw materials of the stripping solution include a strong base and disodium EDTA. In an alkaline environment, the FeMoO4·nH2O composite passivation film will react to generate Fe(OH)3 and MoO4 2- , and the Fe(OH)3 will generate a soluble [Fe(EDTA)] - complex with EDTA in an alkaline environment to promote reliable dissolution and stripping of the FeMoO4·nH2O composite passivation film, thereby ensuring the reliability of subsequent development and improving the morphology of the pre-plating groove after development.

[0043] The present disclosure also provides a preparation method of a solar cell, comprising: coating the composite photosensitive glue on the copper seed layer of the yellow film sheet and printing and exposing; performing edge etching using a strong acid ITO etching solution; cleaning with the stripping solution; developing to form a pre-plating groove; electroplating to form a copper grid line in the pre-plating groove; wherein, the composite photosensitive glue comprises photosensitive glue, sodium molybdate particles, and polyvinylpyrrolidone; wherein the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinylpyrrolidone is 0.05-0.2%, and the balance is photosensitive glue; the stripping solution comprises sodium hydroxide, disodium ethylenediaminetetraacetate, and water; wherein the mass concentration of sodium hydroxide is 30±5 g / L, the mass percentage of disodium ethylenediaminetetraacetate is 0.05-0.2%, and the balance is water.

[0044] The coated composite photosensitive resist contains sodium molybdate particles and polyvinylpyrrolidone. When subsequent edge etching is performed by using a strong acid ITO etching solution, a dense FeMoO4·nH2O composite passivation film is formed to protect the unexposed photosensitive resist, so that the ITO etching solution cannot directly contact the unexposed photosensitive resist, thereby preventing the denaturation of the unexposed photosensitive resist, improving the development difficulty or insufficiency, and improving the problem of ITO etching solution remaining in the unexposed resist film, thereby improving the development effect and improving the problem of resist film remaining in the pre-plating groove. After edge etching, the FeMoO4·nH2O composite passivation film reacts to generate Fe(OH)3 and MoO4 2- , and the generated Fe(OH)3 reacts with EDTA in an alkaline environment to generate a soluble [Fe(EDTA) - ] complex, thereby promoting reliable dissolution and stripping of the FeMoO4·nH2O composite passivation film. In this way, the morphology of the pre-plating groove can be fully improved, the contact stability of the copper seed layer and the electroplated copper can be improved, the adhesion of the electroplated grid line can be improved, the problems of grid line separation and grid breakage (where the proportion of residual copper type grid breakage is less than 0.01%) can be improved, and the yield of the solar cell can be improved.

[0045] Among them, sodium molybdate, as a molybdate, is often used as a corrosion inhibitor and is the main passivation body in the composite photosensitive resist. Polyvinylpyrrolidone can be used as a dispersant to improve the problem of sodium molybdate particles aggregating in the photosensitive resist. In the acidic environment provided by the edge etching process, MoO4 2- will quickly combine with Fe 2+ to generate FeMoO4 precipitates. At the same time, MoO4 2- will be protonated to generate HMoO4 - , which will combine with Fe 2+ and oxidize it to Fe 3+ , forming a composite passivation film with multiple valence states. The reaction equation is as follows: The FeMoO4·nH2O composite passivation film is a continuous film formed by three-dimensional crosslinking of Fe-O-Mo, which has the advantages of defect self-repairing and strong acid resistance.

[0046] The FeMoO4·nH2O composite passivation film will automatically react to generate Fe(OH)3 and MoO4 2- in the alkaline environment provided by the stripping solution. The generated Fe(OH)3 will react with EDTA in an alkaline environment to generate a soluble [Fe(EDTA) - ] complex, thereby promoting dissolution of the film layer. The two-step reaction equations are as follows: Alkaline stripping reaction: ; EDTA complexation reaction (alkaline condition): .

[0047] It should be noted that the thickness of the FeMoO4·nH2O composite passivation film formed is approximately 50-150 nm.

[0048] It should also be noted that the formulation of the strong-acid ITO etching solution is similar to related art, for example, the strong-acid ITO etching solution includes 10 wt% FeCl3, 20 wt% HCl, and the balance being water, or the strong-acid ITO etching solution includes 5 wt% FeCl3, 18 wt% HCl, and the balance being water, or the strong-acid ITO etching solution includes 2 wt% FeCl3, 25 wt% HCl, and the balance being water.

[0049] The components of the photosensitive adhesive are similar to related art, for example, the photosensitive adhesive includes propylene glycol methyl ether acetate, resin, monomers (such as ethylene monomers, propylene monomers, etc.), and initiators (such as organic peroxide benzoyl peroxide, azo compound azobisisobutyronitrile, etc.).

[0050] For example, the composite photosensitive adhesive can include the formulation of the following table:

[0051] Optionally, when cleaning with the stripping solution, the temperature is greater than or equal to 30°C, for example, 30°C, 35°C, 40°C, 45°C, 60°C, 80°C, etc., which is not specifically limited here. Appropriately increasing the temperature for cleaning with the stripping solution is conducive to shortening the stripping time.

[0052] Optionally, the temperature for edge etching is 30-40°C, for example, 30°C, 35°C, 40°C, etc., which is not specifically limited here. Performing edge etching at the above temperature can ensure effective etching of the edges of the cell sheet, and can also ensure reliable and efficient formation of a dense FeMoO4·nH2O composite passivation film to provide reliable protection for the unexposed adhesive film.

[0053] Optionally, the step of cleaning with the stripping solution specifically includes cleaning under ultrasonic conditions.

[0054] Optionally, the frequency of the ultrasonic condition is 40±5 kHz (for example: 35 kHz, 40 kHz, 45 kHz, etc., which is not specifically limited herein), the power is 100±5 W (for example: 95 W, 100 W, 105 W, etc., which is not specifically limited herein), and the stripping liquid is circulated at a circulation flow rate of 100±5 LPM (for example: 95 LPM, 100 LPM, 105 LPM, etc., which is not specifically limited herein). Through the cooperation of ultrasonic and cleaning, the dense FeMoO4·nH2O composite passivation film formed during edge etching can be efficiently and reliably removed, so as to ensure that a pre-plating groove with a good morphology is formed after development, and then to ensure that the subsequent copper grid line has greater bonding force, improves the problems of grid line separation and grid breakage, and improves the yield of the solar cell.

[0055] Optionally, before cleaning with the stripping liquid, overflow water washing can also be performed, and the number of times includes but is not limited to one time, two times, three times, etc.

[0056] Optionally, after the FeMoO4·nH2O composite passivation film is washed away by the stripping liquid, overflow water washing can also be performed again, and the number of times includes but is not limited to one time, two times, three times, etc., as long as the stripping liquid is completely cleaned and removed.

[0057] Optionally, after the FeMoO4·nH2O composite passivation film is washed away by the stripping liquid and overflow water washing, drying (for example: baking for about 10 min) can be performed at a temperature of 40±5℃ (for example: 35℃, 40℃, 45℃, etc., which is not specifically limited herein), so as to ensure that there is no residual moisture on the surface of the cell piece, and then development and subsequent processes are performed.

[0058] The application will be further described in detail below in combination with examples.

[0059] Example 1-1 A preparation method of a solar cell: After the original silicon wafer is cleaned and textured, amorphous silicon is deposited to form a PN junction, and PVD is performed to deposit a TCO conductive film on the front and back surfaces and a PVD-Cu seed layer, thereby obtaining a yellow film piece.

[0060] Enter the copper interconnection process, coat the composite photosensitive glue on the copper seed layer of the yellow film piece, and print and expose; Edge etching is performed by using a strong acid ITO etching liquid; Cleaning is performed by using a stripping liquid; Development is performed to form a pre-plating groove; Copper grid lines are formed by electroplating in the pre-plating groove.

[0061] The composite photosensitive adhesive comprises a photosensitive adhesive, sodium molybdate particles and polyvinylpyrrolidone; the mass percentage of the sodium molybdate particles (particle size of 30 nm) is 0.8%, the mass percentage of the polyvinylpyrrolidone is 0.05%, and the rest is the photosensitive adhesive.

[0062] The stripping solution comprises sodium hydroxide, disodium ethylenediaminetetraacetate and water; the mass concentration of the sodium hydroxide is 25 g / L, the mass percentage of the disodium ethylenediaminetetraacetate is 0.05%, and the rest is water.

[0063] The cleaning with the stripping solution is carried out in a stripping tank, the temperature of the stripping solution is controlled to be 30℃, the ultrasonic frequency is controlled to be 40 kHz, the power is controlled to be 100 W, and the circulation flow rate is controlled to be 100 LPM.

[0064] The temperature of the edge etching is 35℃, and the time is 150 s.

[0065] Example 1-2 Example 1-2 differs from Example 1-1 in that the temperature of the stripping solution is controlled to be 35℃, and the other process parameters refer to those of Example 1-1.

[0066] Example 1-3 Example 1-3 differs from Example 1-1 in that the temperature of the stripping solution is controlled to be 40℃, and the other process parameters refer to those of Example 1-1.

[0067] Example 1-4 Example 1-4 differs from Example 1-1 in that the temperature of the stripping solution is controlled to be 45℃, and the other process parameters refer to those of Example 1-1.

[0068] Example 1-5 Example 1-5 differs from Example 1-1 in that the temperature of the stripping solution is controlled to be 60℃, and the other process parameters refer to those of Example 1-1.

[0069] Example 1-6 Example 1-6 differs from Example 1-1 in that the temperature of the stripping solution is controlled to be 80℃, and the other process parameters refer to those of Example 1-1.

[0070] Example 2-1 A preparation method of a solar cell comprises the following steps: After a raw silicon wafer is cleaned and textured, amorphous silicon is deposited to form a PN junction, and a TCO conductive film and a PVD-Cu seed layer are deposited on the front and back surfaces by PVD to obtain a yellow film wafer.

[0071] In a copper interconnection process, a composite photosensitive adhesive is coated on the copper seed layer of the yellow film wafer, and printing and exposure are performed; Edge etching is performed by using a strong-acid ITO etching solution. cleaning with stripping solution; developing to form a pre-plating groove; electroplating to form a copper grid line in the pre-plating groove.

[0072] The composite photosensitive adhesive comprises a photosensitive adhesive, sodium molybdate particles and polyvinylpyrrolidone; the mass percentage of the sodium molybdate particles (with a particle size of 50 nm) is 1.2%, the mass percentage of the polyvinylpyrrolidone is 0.2%, and the rest is the photosensitive adhesive.

[0073] The stripping solution comprises sodium hydroxide, disodium ethylenediaminetetraacetate and water; the mass concentration of the sodium hydroxide is 35 g / L, the mass percentage of the disodium ethylenediaminetetraacetate is 0.2%, and the rest is water.

[0074] The cleaning with the stripping solution is performed in a stripping tank, the temperature of the stripping solution is controlled to be 30℃, the ultrasonic frequency is controlled to be 35 kHz, the power is controlled to be 105 W, and the circulation flow rate is controlled to be 105 LPM.

[0075] The temperature of the edge etching is 30℃, and the time is 200 s.

[0076] Example 2-2 Example 2-2 differs from Example 2-1 in that the temperature of the stripping solution is controlled to be 35℃, and the other process parameters refer to those of Example 2-1.

[0077] Example 2-3 Example 2-3 differs from Example 2-1 in that the temperature of the stripping solution is controlled to be 40℃, and the other process parameters refer to those of Example 2-1.

[0078] Example 2-4 Example 2-4 differs from Example 2-1 in that the temperature of the stripping solution is controlled to be 45℃, and the other process parameters refer to those of Example 2-1.

[0079] Example 2-5 Example 2-5 differs from Example 2-1 in that the temperature of the stripping solution is controlled to be 60℃, and the other process parameters refer to those of Example 2-1.

[0080] Example 2-6 Example 2-6 differs from Example 2-1 in that the temperature of the stripping solution is controlled to be 80℃, and the other process parameters refer to those of Example 2-1.

[0081] Example 3-1 A preparation method of a solar cell: After cleaning and texturing of a raw silicon wafer, amorphous silicon is deposited to form a PN junction, PVD is performed to deposit a TCO conductive film on the front and back surfaces and a PVD-Cu seed layer, and a yellow film wafer is prepared.

[0082] Into the copper interconnection process, the composite photosensitive glue is coated on the copper seed layer of the yellow film sheet, and printing exposure is performed; Edge etching is performed by using strong acid ITO etching solution; Cleaning is performed by using stripping solution; Development is performed to form a pre-plating groove; The copper grid line is formed by electroplating in the pre-plating groove.

[0083] The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinylpyrrolidone; the mass percentage of the sodium molybdate particles (particle size of 40 nm) is 1.0%, the mass percentage of the polyvinylpyrrolidone is 0.1%, and the rest is photosensitive glue.

[0084] The stripping solution comprises sodium hydroxide, disodium ethylenediaminetetraacetate and water; the mass concentration of the sodium hydroxide is 30 g / L, the mass percentage of the disodium ethylenediaminetetraacetate is 0.1%, and the rest is water.

[0085] The cleaning by using the stripping solution is performed in a stripping tank, the temperature of the stripping solution is controlled to be 30℃, the ultrasonic frequency is controlled to be 45 kHz, the power is controlled to be 95 W, and the circulating flow rate is controlled to be 95 LPM.

[0086] The temperature of the edge etching is 40℃, and the time is 120 s.

[0087] Comparative Example 1 The difference between Comparative Example 1 and Example 1-2 is that the composite photosensitive glue is not used, but the photosensitive glue without sodium molybdate and polyvinylpyrrolidone is used, and the cleaning by using the stripping solution is not performed; the other process parameters refer to Example 1-2. Comparative Example 2-1 The difference between Comparative Example 2-1 and Example 1-1 is that the disodium EDTA is not contained in the stripping solution, and the other process parameters refer to Example 1-1.

[0088] Comparative Example 2-2 The difference between Comparative Example 2-2 and Example 1-2 is that the disodium EDTA is not contained in the stripping solution, and the other process parameters refer to Example 1-2.

[0089] Comparative Example 2-3 The difference between Comparative Example 2-3 and Example 1-3 is that the disodium EDTA is not contained in the stripping solution, and the other process parameters refer to Example 1-3.

[0090] Comparative Example 2-4 The difference between Comparative Example 2-4 and Example 1-4 is that the disodium EDTA is not contained in the stripping solution, and the other process parameters refer to Example 1-4.

[0091] Comparative Example 2-5 Comparative Example 2-5 and Example 1-5 differ in that the stripping solution does not contain disodium EDTA, and other process parameters refer to Example 1-5.

[0092] Comparative Example 2-6 Comparative Example 2-6 and Example 1-6 differ in that the stripping solution does not contain disodium EDTA, and other process parameters refer to Example 1-6.

[0093] The grooves of the battery pieces of Example 1-2 and Comparative Example 1 after development were photographed for detection, and the results are shown in Figure 1 , Figure 2 ; at the same time, the grid line shedding photos of the battery pieces of Comparative Example 1 were taken, as shown in Figure 3 .

[0094] The grid shedding and residual copper type grid breaking of the battery pieces of Example 1-2 and Comparative Example 1 were detected and the proportion was counted, and the results are shown in Figure 4 .

[0095] According to the results of Figures 1-4 , in the preparation method of Comparative Example 1, the ITO etching solution directly contacts the photosensitive adhesive film, the ITO etching solution can penetrate into the unexposed adhesive film area, and the strong oxidizing and strong acidic ITO etching solution can directly cause the adhesive film to denature, making it difficult to be washed off by the alkaline developer in the unexposed area, affecting the development effect; at the same time, the strong acidic ITO etching solution that penetrates can directly react with the alkaline developer, consuming the developer while reducing the development effect, causing serious residual glue at the bottom of the groove after development as shown in Figure 2 .

[0096] The direct consequence of the residual glue at the bottom of the groove is to affect the contact between the PVD copper seed layer and the electroplated copper, and the final result is to cause the grid line to shed in a mesh shape, as shown in Figure 3 , which directly affects the yield of the battery piece. The proportion of grid shedding and residual copper type grid breaking on the battery piece is higher, as shown in Figure 4 .

[0097] Using the preparation method of Example 1-2 of the present application, the residual glue in the groove can be effectively reduced, as shown in Figure 1 , and the proportion of grid shedding and residual copper type grid breaking on the battery piece can be effectively reduced, as shown in Figure 4 .

[0098] The stripping time of Comparative Example 1-1~Example 1-6, Example 2-1~Example 2-6, and Comparative Example 2-1~Comparative Example 2-6 was compared, and the results are shown in Figure 5 .

[0099] According to the results of Figure 5It can be seen that the influence of temperature on the stripping time conforms to the Arrhenius equation, the higher the temperature, the shorter the stripping time. Moreover, EDTA as a complexing agent is important for the dissolution of the composite passivation layer, and the addition of different amounts of EDTA can greatly reduce the dissolution stripping time of the passivation layer.

[0100] In summary, the composite photosensitive glue and the stripping solution of the present application can be used to prepare solar cells. The composite photosensitive glue can be coated on the copper seed layer of the yellow film sheet, so that when the edge etching is carried out by using a strong acidic ITO etching solution subsequently, a dense FeMoO4·nH2O composite passivation film is formed to block the attack of the ITO etching solution on the unexposed glue film, i.e., to improve the problem of the degeneration of the unexposed glue film under the action of the ITO etching solution, and to reduce the problem of the residual ITO etching solution in the unexposed glue film. Then, the FeMoO4·nH2O composite passivation film is dissolved and stripped by using the stripping solution, so as to improve the problem of the poor appearance of the pre-plating groove formed by subsequent development, and to improve the contact stability of the copper seed layer and the plated copper, improve the adhesion of the plated grid lines, improve the problems of grid line separation and broken grid, and improve the yield of the solar cells.

[0101] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite photosensitive paste for preparing a solar cell, characterized by, The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinyl pyrrolidone; wherein, the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinyl pyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue. The particle size of the sodium molybdate particles is 30-50 nm.

2. The composite photosensitive paste for preparing a solar cell according to claim 1, wherein The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinyl pyrrolidone; wherein, the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinyl pyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue.

3. A stripping solution for preparing a solar cell, characterized by, The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinyl pyrrolidone; wherein, the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinyl pyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue. The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinyl pyrrolidone; wherein, the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinyl pyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue.

4. A method for producing a solar cell, characterized by, The composite photosensitive glue comprises photosensitive glue, sodium molybdate particles and polyvinyl pyrrolidone; wherein, the mass percentage of the sodium molybdate particles is 0.8-1.2%, the mass percentage of the polyvinyl pyrrolidone is 0.05-0.2%, and the rest is the photosensitive glue. The particle size of the sodium molybdate particles is 30-50 nm. The temperature of the cleaning with the stripping solution is greater than or equal to 30℃. The temperature of the edge etching is 30-40℃. The step of cleaning with the stripping solution specifically comprises cleaning under ultrasonic condition. The frequency of the ultrasonic condition is 40±5 kHz, the power is 100±5 W, and the stripping solution is circulated with a circulation flow rate of 100±5 LPM. The solar cell is prepared by the preparation method of any one of claims 4-9. ​ 5. The method of producing a solar cell according to claim 4, wherein ​ 6. The method of producing a solar cell according to claim 4, wherein ​ 7. The method of producing a solar cell according to claim 4, wherein ​ 8. The method of producing a solar cell according to claim 4, wherein ​ 9. The method of producing a solar cell according to claim 8, wherein ​ 10. A solar cell, characterized by, ​

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