Etching method of thin film solar cell substrate
By forming an oxide layer and a water film protective layer on the surface of the functional film layer of the cadmium telluride thin film solar cell, the problem of the functional film layer being destroyed during the etching process is solved, and the product pass rate and production stability are improved.
Patent Information
- Application Number
- CN202510049507.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-13
- Publication Date
- 2025-05-09
AI Technical Summary
In the prior art, during the male etching process of cadmium telluride thin film solar cells, it is difficult to completely avoid the damage to the functional film layer by strong corrosive solutions, resulting in a decrease in the pass rate of thin film solar cells.
On the surface of the cadmium telluride functional film layer of the thin-film solar cell, an oxide layer is first formed, and then the water film is sprayed through a two-fluid spraying process to form a double protective layer to prevent damage to the functional film layer by the etching solution and volatile acids.
It effectively protects the functional film layer of cadmium telluride from being damaged by the etching environment, significantly improves the production pass rate of thin-film solar cells, and does not affect subsequent processes.
Smart Images
Figure CN119967935A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of preparing thin-film solar cells, and in particular relates to a method for etching a thin-film solar cell substrate. Background Art
[0002] Cadmium telluride thin-film solar cells refer to photovoltaic cells that are constructed by depositing a layer of materials with photoelectric conversion functions such as cadmium telluride and cadmium sulfide (cadmium telluride functional film layer) on a glass substrate or other flexible substrate. In the production process of cadmium telluride thin-film solar cells, the surface of the solar panel close to the substrate (the side irradiated by sunlight) after the functional film layer is electroplated is called the positive side. The positive side etching process is a very important step in the preparation of cadmium telluride thin-film solar cells. Its main function is to use concentrated nitric acid to etch away the residue on the positive side to prevent the residue on the positive side (such as cadmium telluride, cadmium sulfide, etc.) from connecting to the functional film layer and causing a short circuit. Further cleaning the film layer on the positive side can effectively improve the light transmittance of the positive side.
[0003] In the prior art, after the cadmium telluride functional film layer is plated on the cell, it is activated by an activation furnace, and finally, the cell is placed in the positive side etching equipment for etching. The cell is transferred by rollers in the etching equipment, moved horizontally, and passed into the etching tank. The concentrated nitric acid solution in the etching tank just covers the rollers, and the positive side is immersed in the concentrated nitric acid solution, so that the concentrated nitric acid fully etches the residue on the positive side; at the same time, a positive pressure blow is given above the etching tank to reduce the solution fluctuation caused by the movement of the cell in the solution, which causes the solution to splash onto the cadmium telluride functional film layer, or to avoid the nitric acid condensation beads from dripping onto the surface of the cadmium telluride functional film layer due to the volatilization of strong nitric acid, thereby destroying the functional film layer. However, most areas of the cadmium telluride functional film layer are still exposed to the large environment of the etching process, and the positive pressure blowing method cannot completely prevent the strong corrosive solution or condensation beads from corroding the cadmium telluride functional film layer, which still leads to a significant decrease in the qualified rate of thin-film solar cells in the etching stage of the substrate surface. Summary of the invention
[0004] In view of the problem that the cadmium telluride functional film layer is damaged by corrosive substances during the etching stage of the substrate surface of the thin-film solar cell involved above, resulting in a decrease in the qualified rate thereof, the present invention provides a method for etching a thin-film solar cell substrate, which can effectively protect the cadmium telluride functional film layer from being damaged by the etching environment, thereby further improving the qualified rate of the production of thin-film solar cells.
[0005] To achieve the above purpose, the following technical solutions are specifically included:
[0006] A method for etching a thin-film solar cell substrate comprises the following steps:
[0007] (1) preparing a thin-film solar cell, wherein the thin-film solar cell comprises a substrate and a functional film layer containing cadmium telluride on the substrate;
[0008] (2) performing activation and oxidation pretreatment on the thin-film solar cell in sequence;
[0009] (3) spraying a water film on the surface of the functional film layer containing cadmium telluride in the thin-film solar cell by a two-fluid spraying process;
[0010] (4) etching the substrate in the thin film solar cell using an etching solution;
[0011] (5) The thin film solar cell is then dried, immersed in an acidic aqueous solution and washed with water in sequence.
[0012] A thin-film solar cell to be etched after electroplating cadmium telluride includes a substrate and a functional film layer containing cadmium telluride on the substrate. Due to the aforementioned process, there are residues such as cadmium telluride and cadmium sulfide on the surface of the substrate, and the residues on the surface of the substrate need to be etched away. However, when etching the surface of the substrate, it is necessary to avoid damaging or destroying the functional film layer. In this regard, before etching the surface of the substrate, the present invention sequentially introduces an oxide layer and a water film layer on the surface of the functional film layer containing cadmium telluride to protect it and prevent it from being damaged in the subsequent substrate etching stage. Specifically, after the activation treatment of the thin-film solar cell, the thin-film solar cell is subjected to oxidation pretreatment, so that the surface of the functional film layer containing cadmium telluride is oxidized, and a passivation oxide layer is formed on its surface, and the oxide layer can improve the hydrophilicity of the surface of the functional film layer containing cadmium telluride; then a water film is sprayed on the surface of the functional film layer containing cadmium telluride, and the hydrophilicity of the surface is improved due to the pre-oxidation treatment in the previous step, and the formed water film has good adhesion and high stability on its surface, and can well protect the functional film layer; when etching the substrate, the water film layer can effectively prevent the etching solution from sputtering or droplets formed by condensation after the etching solution evaporates and falls on the functional film layer, and because the functional film layer has dual protection of the water film layer and the oxide layer, even nitric acid volatilized in the air will not cause any damage to the functional film layer, which greatly improves the qualified rate of the etching stage in the production of thin-film solar cells. In addition, after etching, by drying and removing the oxide layer on the surface of the functional film layer, the water film layer and the oxide layer will not affect the next process.
[0013] Preferably, in step (1), the substrate comprises a glass substrate.
[0014] Glass substrates have low cost, good light transmittance and stability, making them ideal substrates for thin-film solar cells.
[0015] Preferably, the thickness of the substrate is 3-5 mm, and the thickness of the functional film layer containing cadmium telluride is 2-10 μm.
[0016] Preferably, in step (1), the thin film solar cell is a thin film solar cell that is subjected to substrate etching after cadmium telluride electroplating.
[0017] Preferably, in step (2), the activation temperature is 400-500° C., and the activation time is 10-60 min.
[0018] Preferably, in step (2), the activation atmosphere is an inert gas atmosphere, and the inert gas includes at least one of nitrogen, argon and helium.
[0019] The activation step in the production of thin-film solar cells is to improve the crystallinity of the CdTe-containing functional film layer, reduce the interface defects between CdTe and CdS, enhance the degree of mutual diffusion between CdS and CdTe, and reduce the lattice mismatch. If there are doping elements such as Cl in the functional film layer, activation helps the formation of Cl vacancies, and doping atoms such as Cl can better enter the CdTe lattice to achieve P-type doping and improve electrical properties.
[0020] Preferably, in step (2), the temperature of the oxidation pretreatment is 400-500° C., the time of the oxidation pretreatment is 1-5 min, and the atmosphere of the oxidation pretreatment is a mixed atmosphere containing 1-10% by volume of oxygen and 99-90% by volume of an inert gas.
[0021] Preferably, in step (2), after the oxidation pretreatment, the surface of the functional film layer containing cadmium telluride contains an oxide layer of 10-50 nm.
[0022] After the surface of the functional film layer of cadmium telluride is oxidized, the oxide layer of oxides such as CdO is formed, which usually has a high surface hydrophilicity. This is because the hydroxyl group (-OH) and other hydrophilic groups on the surface of the oxide can form hydrogen bonds with water molecules, thereby increasing the hydrophilicity of the surface. Moreover, the surface energy after oxidation is usually higher, and it is easier to adsorb water molecules, showing stronger hydrophilicity. The oxidation pretreatment time of the present invention is short, and the temperature of the oxidation pretreatment can be consistent with the temperature of the activation stage. Therefore, an oxygen-containing atmosphere can be directly introduced into the final stage of the activation stage for oxidation pretreatment, which not only saves time, but also can complete surface oxidation in the activation stage. The surface oxide layer is more uniform and dense, further improving the hydrophilicity of the surface of the functional layer, and providing a good foundation for the subsequent attachment of the water film.
[0023] Preferably, in step (3), in the two-fluid spraying process, compressed air is added while spraying water, so that the sprayed water droplets are in an atomized form.
[0024] In the two-fluid spraying process, water flow and compressed air are used as two fluids of the process, which can make the sprayed water droplets into an atomized form, and the water droplets are more delicate and compact, making the uniformity of the water film better. Because the oxide layer is highly hydrophilic, and the surface tension of the water itself makes the structure of this water film stable, in the absence of external force, the water film will form a barrier to protect the functional film layer below.
[0025] Preferably, in step (3), the thickness of the water film is 100-200 μm.
[0026] Preferably, in step (4), the etching solution is an aqueous solution comprising 35-45 wt. % nitric acid and 35-45 wt. % phosphoric acid.
[0027] Entering the etching process section, the etching solution is generally a concentrated nitric acid solution. Since the mass fraction of nitric acid sold on the market is about 68%, it is extremely volatile, and the volatility of nitric acid increases with the increase of temperature. After the volatilized nitric acid is inhaled into the human body, it is very harmful to the human body. In the present invention, an aqueous solution with a concentration of 35-45wt.% nitric acid and 35-45wt.% phosphoric acid is set in the workbench during the etching stage, which can not only meet the etching requirements, but also avoid the conventional use of only nitric acid as an etching solution. The high concentration of nitric acid causes its excessive volatilization, causing harm to workers. At the same time, it also reduces the amount of nitric acid used, which can save costs.
[0028] Preferably, in step (4), the etching method is: placing the thin-film solar cell in a conveying device and making its substrate contact the etching liquid for etching, and the conveying rate of the substrate is 1-3 m / min.
[0029] The thin-film solar cell coated with water film is placed with one side of its substrate in a conveying device, and is conveyed to the etching tank by the conveying device. The conveying speed is set to 1-3m / min, which can not only avoid the conveying speed being too fast and unable to ensure the adequacy of etching, but also avoid the cost increase or excessive corrosion caused by too slow speed.
[0030] Preferably, in step (4), the etching temperature is 40-50°C.
[0031] Under the above-mentioned relatively low working temperature conditions, the etching requirements can be met while avoiding excessive temperature. The acid in the etching solution may volatilize excessively due to the high temperature, causing harm to the workers.
[0032] Preferably, in step (5), the drying is carried out by air knife drying.
[0033] Air knife drying can be used to easily and quickly remove the water film on the substrate of thin-film solar cells.
[0034] Preferably, in step (5), the acidic aqueous solution comprises 2-8 wt.% nitric acid and 2-8 wt.% phosphoric acid.
[0035] Using a low-concentration acidic aqueous solution to immerse the thin-film solar cell substrate can simply remove the oxide layer on the surface of the functional film layer containing cadmium telluride, avoiding affecting subsequent processes, and because the concentration of the acidic aqueous solution is low, further corrosion of the functional film layer can be avoided.
[0036] Preferably, in step (5), the immersion time is 10 s-5 min.
[0037] Compared with the prior art, the present invention has the following beneficial effects: before etching the surface of the thin-film solar cell substrate, the present invention sequentially introduces an oxide layer and a water film layer on the surface of the functional film layer containing cadmium telluride to protect it, thereby avoiding the loss or even destruction of the film layer caused by the corrosive substances present in the subsequent substrate etching stage. Without affecting the continuity of the entire process flow, the present invention can greatly improve the stability and product qualification rate in the production of thin-film solar cells, and greatly improve the continuous productivity of the production line. BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 The present invention is a flow chart of the etching method of the thin film solar cell substrate.
[0039] Figure 2 Schematic diagram of forming a water film on the functional film layer in the two-fluid spraying process.
[0040] Figure 3 Schematic diagram of etching of thin-film solar cell substrate in etching process, wherein: 1. roller; 2. etching solution; 3. glass substrate; 4. CdTe functional film layer; 5. oxide layer; 6. water film.
[0041] Figure 4 This is a picture of the oxide layer surface on the surface of the CdTe functional film layer obtained by taking a 3D microscope.
[0042] Figure 5 This is a cross-sectional image of the oxide layer on the surface of the CdTe functional film layer taken using a 3D microscope.
[0043] Figure 6 Schematic diagram of the water drop angle test on the surface of the CdTe functional film layer after activation without oxidation pretreatment, the water contact angle is 70-80°.
[0044] Figure 7 This is a schematic diagram of a water drop angle test on the surface of the CdTe functional film layer after oxidation pretreatment after activation in Example 1. The water contact angle is 10-20°. DETAILED DESCRIPTION
[0045] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.
[0046] Example 1
[0047] A method for etching a thin film solar cell substrate, the flow chart is as follows Figure 1 As shown, the specific steps include:
[0048] (1) preparing a thin-film solar cell for etching a substrate (positive side) after electroplating cadmium telluride, the thin-film solar cell comprising a glass substrate and a functional film layer containing cadmium telluride on the substrate, wherein the glass substrate has a thickness of about 3.2 mm, the functional film layer containing cadmium telluride has a thickness of about 4 μm, and the functional film layer contains substances such as CdTe, CdS and CdCl2;
[0049] (2) placing the thin film solar cell in a high temperature furnace and activating it at 450° C. for 20 min in a nitrogen atmosphere. After activation, the mixture of 5 vol% oxygen and 95 vol% argon by volume is directly injected without cooling. After the mixture is injected, it is kept for 3 min for oxidation pretreatment, so that the surface of the CdTe functional film layer undergoes an oxidation reaction under high temperature conditions, thereby generating an oxide layer with a thickness of 20 to 30 nm. After being taken out of the furnace, it is cooled to room temperature.
[0050] (3) After the activation furnace process is completed, a water spraying system is set in front of the etching tank. The battery cell is transferred by rollers in the water spraying system and moves horizontally. The water spraying system is used to spray deionized water on the oxidized battery functional layer of the battery cell. The spraying system uses a two-fluid spraying process. Compressed air is added while spraying water, which can make the sprayed water droplets atomized. The water droplets are more delicate and compact, and a water film protective layer with a thickness of about 100 to 200 μm is formed more evenly on the surface of the battery panel functional layer. The schematic diagram is shown as follows Figure 2 As shown;
[0051] (4) After the cell is covered with the water film layer, it is transferred horizontally through rollers in the etching equipment and passed into the etching tank. The etching tank is set with an acidic aqueous solution containing 40wt% HNO3 and 40wt% H3PO4 as an etching solution. The etching solution just covers the rollers and immerses the substrate in the etching solution so that the etching solution can fully etch away the residue on the surface of the substrate. The temperature of the substrate etching solution in this process section is 45°C, and the transmission speed is set to 2m / min. The schematic diagram is shown in FIG. Figure 3 As shown;
[0052] (5) After etching, the water film is blown dry with an air knife, and then the battery cell is immersed in an acidic aqueous solution containing 5wt% HNO3 and 5% H3PO4 (abbreviated as NP) for 1 min. The oxide layer on the functional film layer is cleaned with a low concentration of acidic solution, and then washed with water to expose the CdTe functional film layer to ensure that the next process is not affected.
[0053] The water drop tester was used to test Example 1. The test results are as follows: Figure 7 As shown. It can be seen that the surface of the CdTe functional film layer undergoes an oxidation reaction under high temperature conditions, thereby generating a very thin oxide layer, which is denser than the CdTe functional film layer (such as Figure 4 As shown in Figure 2, the oxide layer has a passivation effect, so that oxygen cannot continue to penetrate the CdTe layer under the oxide layer for oxidation, and the oxide layer has an irregular shape (such as Figure 5 As shown), the hydrophilicity of the membrane surface is greatly improved. Through the water drop angle test, it can be seen that when no oxidation pretreatment is performed, the water drop angle test angle of the functional membrane surface is 70-80°; after the oxidation pretreatment with an oxygen content of 5% in Example 1, the water drop angle test angle of the functional membrane surface is 10-20°. The smaller the water contact angle, the better the hydrophilicity. It can be seen that after the injection of 5% oxygen oxidation pretreatment, the hydrophilicity of the membrane surface will be better than that of the membrane surface without oxygen pretreatment.
[0054] At the same time, the inventors have also tried not to perform oxidation pretreatment on the surface of the CdTe functional film layer (i.e., no oxygen is introduced after activation). The surface of the CdTe functional film layer is not hydrophilic, and the water film formed on the surface of the thin-film solar cell cannot be sprayed in the two-fluid spraying process. The water film is uneven and discontinuous, and the structure of the formed water film is not stable enough. During the transmission of the thin-film solar cell, due to inertia, vibration and other reasons, the water film slides off the surface of the thin-film solar cell, causing the CdTe functional film layer to be exposed to the etching process environment, and part of the CdTe functional film layer is etched away, causing irreversible damage to the functional structure and appearance of the entire battery, making it impossible to continue to use.
[0055] Due to the oxidation pretreatment in the previous step, the hydrophilicity of the surface is improved. Then, a water film is sprayed on the surface of the functional film layer containing cadmium telluride. The formed water film has good adhesion and high stability on its surface, and can well protect the functional film layer. When etching the substrate, the water film layer can effectively prevent the etching solution from sputtering or droplets formed by condensation after the etching solution evaporates and falls on the functional film layer. Moreover, since the functional film layer has the dual protection of the water film layer and the oxide layer, even nitric acid volatilized in the air will not cause any damage to the functional film layer, which greatly improves the qualified rate of the etching stage in the production of thin-film solar cells. In addition, after etching, by drying and removing the oxide layer on the surface of the functional film layer, the water film layer and the oxide layer will not affect the next step.
[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.
Claims
1. A method for etching a thin film solar cell substrate, characterized in that: The steps include: (1) preparing a thin-film solar cell, wherein the thin-film solar cell comprises a substrate and a functional film layer containing cadmium telluride on the substrate; (2) performing activation and oxidation pretreatment on the thin-film solar cell in sequence; (3) spraying a water film on the surface of the functional film layer containing cadmium telluride in the thin-film solar cell by a two-fluid spraying process; (4) etching the substrate in the thin film solar cell using an etching solution; (5) The thin film solar cell is then dried, immersed in an acidic aqueous solution and washed with water in sequence.
2. The etching method for a thin film solar cell substrate according to claim 1, characterized in that: In step (1), the substrate comprises a glass substrate, the thin film solar cell is a thin film solar cell that is electroplated with cadmium telluride and then etched; the thickness of the substrate is 3-5 mm, and the thickness of the functional film layer containing cadmium telluride is 2-10 μm.
3. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (2), the activation temperature is 400-500° C., the activation time is 10-60 min, and the activation atmosphere is an inert gas atmosphere.
4. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (2), the temperature of the oxidation pretreatment is 400-500°C, the time of the oxidation pretreatment is 1-5 minutes, and the atmosphere of the oxidation pretreatment is a mixed atmosphere containing 1-10% by volume of oxygen and 99-90% by volume of an inert gas; after the oxidation pretreatment, the surface of the functional film layer containing cadmium telluride contains an oxide layer of 10-50 nm.
5. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (3), in the two-fluid spraying process, compressed air is added while spraying water, so that the sprayed water droplets are in an atomized form.
6. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (3), the thickness of the water film is 100-200 μm.
7. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (4), the etching solution is an aqueous solution comprising 35-45wt.% nitric acid and 35-45wt.% phosphoric acid.
8. The method for etching a thin film solar cell substrate according to claim 1, characterized in that: In step (4), the etching method is: placing the thin-film solar cell in a conveying device and making its substrate contact the etching liquid for etching, and the conveying rate of the substrate is 1-3 m / min.
9. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (4), the etching temperature is 40-50°C.
10. The etching method for a thin-film solar cell substrate according to claim 1, characterized in that: In step (5), the drying is carried out by air knife drying, and the acidic aqueous solution includes 2-8 wt. % nitric acid and 2-8 wt. % phosphoric acid.