Back contact solar cell and preparation method thereof
The large-scale stacked silicon wafers prepared through multi-step cleaning and alkali casting processes solve the problem that single silicon wafers cannot provide a good interface, achieve efficient polysilicon growth and low contact resistance, and improve the performance and production efficiency of solar cells.
Patent Information
- Application Number
- CN202510155658.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-05-06
AI Technical Summary
Single-map silicon wafers cannot provide a good interface for the growth of polysilicon, resulting in poor performance PN junctions and high contact resistance.
The preparation method of large-scale stacked tower silicon wafers using multi-step cleaning and alkali casting processes includes pre-alkali washing, pre-alkali washing, water washing, post-alkali washing, ozone washing, pickling and water removal treatment, and optimize the alkali casting process to form an excellent interface.
It improves the growth interface quality of polysilicon, reduces contact resistance, improves the conversion efficiency and service life of solar cells, and at the same time shortens the process time, improves production efficiency and reduces production costs.
Smart Images
Figure CN119947303A_ABST
Abstract
Description
[0001] This application is a divisional application of the Chinese invention patent application with application number 202410362286.1, application date March 27, 2024, and invention name "Large and small stacked tower base silicon wafers and preparation methods thereof". Technical Field
[0002] The present application belongs to the field of solar cells, and specifically relates to a back-contact solar cell and a method for preparing the same. Background Art
[0003] With the depletion of fossil energy and environmental pollution, there is an urgent need for a clean, pollution-free, and sustainable green energy. Solar cells are particularly important as the most promising sustainable clean energy. Therefore, the industry has conducted extensive and continuous research on solar cells. Back contact cells have received more attention from the industry due to their high conversion efficiency. Among them, the technical core of BC cells lies mainly in the preparation of excellent PN junctions on the back of silicon wafers, and covering them with aluminum oxide or silicon oxide films to increase the cell opening voltage, passivate the back surface, and improve the long-wave response, thereby improving the cell conversion efficiency. Among them, silicon wafers are the main material of solar cells, and their quality directly affects the conversion efficiency of solar cells.
[0004] In the process of preparing silicon wafers, some solar cells in the related art use alkaline polishing to remove the damaged layer on the surface of the silicon wafer to prepare a single-tower-based silicon wafer, and then carry out subsequent process steps on this basis to prepare a solar cell with better performance.
[0005] However, the above-mentioned single-tower-based silicon wafer cannot provide a good interface for the growth of polycrystalline silicon, so that a PN junction with better performance cannot be prepared, and the contact resistance with the slurry is relatively high, and the surface quality of the silicon wafer is poor. Summary of the invention
[0006] The purpose of the embodiments of the present application is to provide a large and small stacked tower base silicon wafer and a preparation method thereof, which can at least solve the problem that a single tower base silicon wafer cannot provide a good interface for the growth of polysilicon.
[0007] In order to solve the above technical problems, this application is implemented as follows:
[0008] The present application provides a method for preparing large and small stacked tower base silicon wafers, the preparation method comprising:
[0009] Pre-alkaline washing: using a cleaning solution to clean the original silicon wafer to obtain a first base silicon wafer;
[0010] Pre-alkali polishing: using a first alkali polishing solution to perform a first alkali polishing treatment on the first base silicon wafer to obtain a second base silicon wafer;
[0011] One water washing: washing the second base silicon wafer with deionized water to obtain a third base silicon wafer;
[0012] Post-alkali polishing: performing a second alkali polishing treatment on the third base silicon wafer using a second alkali polishing solution to obtain a fourth base silicon wafer;
[0013] Secondary water washing: washing the fourth base silicon wafer with deionized water to obtain a fifth base silicon wafer;
[0014] Ozone cleaning: cleaning the fifth base silicon wafer with ozone liquid to obtain a sixth base silicon wafer;
[0015] Pickling: pickling the sixth base silicon wafer with a pickling solution to obtain a seventh base silicon wafer;
[0016] Three water washings: washing the seventh base silicon wafer with deionized water to obtain an eighth base silicon wafer;
[0017] Dehydration treatment: performing a slow pulling dehydration treatment on the eighth base silicon wafer to obtain a ninth base silicon wafer;
[0018] Drying: Dry the ninth base silicon wafer to obtain large and small stacked tower base silicon wafers.
[0019] The embodiment of the present application also provides a large and small stacked tower base silicon wafer, which is prepared by the above-mentioned preparation method of the large and small stacked tower base silicon wafer.
[0020] The embodiment of the present application adopts a method for preparing large and small stacked tower base silicon wafers, which can prepare large and small stacked tower bases with excellent interfaces, which is beneficial to the growth of polycrystalline silicon. On this basis, a PN junction with better performance can be prepared, and the contact area with the slurry is increased, thereby reducing the contact resistance and improving the conversion efficiency and service life of the solar cell; and the preparation method in the embodiment of the present application can also be beneficial to improving the surface quality of the silicon wafer, reducing the defect density, and can better support the growth of polycrystalline silicon and improve the performance of the battery; in addition, the preparation method in the embodiment of the present application also optimizes the alkali polishing process, which can effectively shorten the time of the alkali polishing process, improve production efficiency, and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a schematic diagram of a single tower base in the related art;
[0022] Figure 2 A schematic diagram of large and small stacked tower bases disclosed in an embodiment of the present application;
[0023] Figure 3 This is a flow chart of a method for preparing large and small stacked tower base silicon wafers disclosed in an embodiment of the present application. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0025] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.
[0026] The embodiments of the present application are described in detail below through specific embodiments and their application scenarios in conjunction with the accompanying drawings.
[0027] refer to Figure 2 and Figure 3 The present application embodiment discloses a method for preparing large and small stacked tower base silicon wafers, which is used to prepare large and small stacked tower base silicon wafers. The disclosed preparation method includes:
[0028] Pre-alkaline washing: using a cleaning solution to clean the original silicon wafer to obtain a first base silicon wafer;
[0029] Pre-alkali polishing: using a first alkali polishing liquid to perform a first alkali polishing treatment on the first base silicon wafer to obtain a second base silicon wafer;
[0030] One water washing: using deionized water to wash the second base silicon wafer to obtain a third base silicon wafer;
[0031] Post-alkali polishing: the third base silicon wafer is also subjected to a second alkali polishing treatment using the second alkali polishing to obtain a fourth base silicon wafer;
[0032] Secondary water washing: using deionized water to wash the fourth base silicon wafer to obtain a fifth base silicon wafer;
[0033] Ozone cleaning: cleaning the fifth base silicon wafer with ozone liquid to obtain a sixth base silicon wafer;
[0034] Pickling: pickling the sixth base silicon wafer with a pickling solution to obtain a seventh base silicon wafer;
[0035] Three water washings: washing the seventh base silicon wafer with deionized water to obtain an eighth base silicon wafer;
[0036] Dehydration treatment: performing a slow pulling dehydration treatment on the eighth base silicon wafer to obtain a ninth base silicon wafer;
[0037] Drying: Dry the ninth base silicon wafer to obtain large and small stacked tower base silicon wafers.
[0038] Based on the above steps, the embodiment of the present application adopts a method for preparing large and small stacked tower base silicon wafers, which can prepare large and small stacked tower bases with excellent interfaces, which is conducive to the growth of polycrystalline silicon. On this basis, a PN junction with better performance can be prepared, and the contact area with the slurry is increased, thereby reducing the contact resistance and improving the conversion efficiency and service life of solar cells.
[0039] The preparation method in the embodiment of the present application can also help improve the surface quality of silicon wafers, reduce defect density, better support the growth of polycrystalline silicon, and improve the performance of batteries.
[0040] The preparation method in the embodiment of the present application also optimizes the alkali polishing process, which can effectively shorten the time of the alkali polishing process, improve production efficiency and reduce production costs.
[0041] Optionally, a pre-alkali wash comprises:
[0042] The time for cleaning the original silicon wafer with the cleaning solution is 50s~200s, for example, 50s, 100s, 150s, 200s, etc.; the temperature of the cleaning solution is 40℃~70℃, for example, 40℃, 50℃, 60℃, 70℃, etc.
[0043] The components of the cleaning liquid may include: water (DI), sodium hydroxide (NaOH) and hydrogen peroxide (H2O2). Among them, in the cleaning liquid, the proportion of water is 90% to 98%, for example, 90%, 93%, 95%, 98%, etc.; the proportion of sodium hydroxide is 0.5% to 2%, for example, 0.5%, 1%, 1.5%, 2%, etc.; the proportion of hydrogen peroxide is 2% to 8%, for example, 2%, 4%, 6%, 8%, etc. It should be noted here that the above proportions can be expressed as volume proportions.
[0044] Preferably, in the cleaning solution, the volume ratio of water, sodium hydroxide and hydrogen peroxide is 420 L: 8 L: 32 L. Of course, other ratios are also possible and are not specifically limited here.
[0045] Optionally, the time of the first alkali polishing treatment is 180s to 200s, for example, 180s, 185s, 190s, 195s, 200s, etc.; the temperature of the first alkali polishing solution is 75°C to 80°C, for example, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, etc.
[0046] The components of the first alkaline polishing solution may include: water (DI), sodium hydroxide (NaOH) and additives (ADD). Among them, the proportion of water is 90% to 95%, for example, 90%, 91%, 92%, 93%, 94%, 95%, etc.; the proportion of sodium hydroxide is 4% to 8%, for example, 4%, 5%, 6%, 7%, 8%, etc.; the proportion of additives is 0.5% to 1.5%, for example, 0.5%, 0.75%, 1%, 1.25%, 1.5%, etc. It should be noted here that the above proportions can represent volume proportions.
[0047] Preferably, in the first alkaline polishing solution, the volume ratio of water, sodium hydroxide and additive is 425 L: 30 L: 5.5 L. Of course, other ratios are also possible and are not specifically limited here.
[0048] Optionally, the components of the additives used in the pre-alkali polishing process may include water, a reaction catalyst, a surfactant, a corrosion inhibitor and an inorganic salt.
[0049] Optionally, the time for one water washing is 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.
[0050] Optionally, the time of the second alkali polishing treatment is 80s to 120s, for example, 80s, 90s, 100s, 110s, 120s, etc.; the temperature of the second alkali polishing solution is 78°C to 84°C, for example, 78°C, 80°C, 82°C, 84°C, etc.
[0051] The components of the second alkaline polishing liquid may include: water (DI), sodium hydroxide (NaOH) and additives (ADD). Among them, the proportion of water is 80% to 85%, for example, 80%, 81%, 82%, 83%, 84%, 85%, etc.; the proportion of sodium hydroxide is 14% to 18%, for example, 14%, 15%, 16%, 17%, 18%, etc.; the proportion of additives is 0.8% to 1.2%, for example, 0.8%, 0.9%, 1%, 1.1%, 1.2%, etc. It should be noted here that the above proportions can represent volume proportions.
[0052] Preferably, in the second alkaline polishing solution, the volume ratio of water, sodium hydroxide and additive is 380 L: 75 L: 4.5 L. Of course, other ratios are also possible and are not specifically limited here.
[0053] Optionally, the components of the additives used in the post-alkali polishing process may include water, a reaction catalyst, a surfactant, a corrosion inhibitor and an inorganic salt.
[0054] Optionally, the secondary water washing time is 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.
[0055] Optionally, the ozone cleaning time is 200s to 800s, for example, 200s, 400s, 600s, 800s, etc.
[0056] The components of the ozone liquid may include water, ozone and hydrochloric acid. The proportion of water is 99.8% to 99.95%, for example, 99.8%, 99.85%, 99.9%, 99.95%, etc. The proportion of hydrochloric acid is 0.05% to 0.2%, for example, 0.05%, 0.1%, 0.15%, 0.2%, etc. In addition, the concentration of ozone may be 20ppm to 60ppm, for example, 20ppm, 40ppm, 50ppm, 60ppm, etc.
[0057] Preferably, the volume ratio of water to hydrochloric acid is 460L:0.5L, and the concentration of ozone can be 45ppm. Of course, other ratios are also possible, which are not specifically limited here.
[0058] Optionally, the pickling time is 100s to 250s, for example, 100s, 150s, 200s, 250s, etc.
[0059] The components of the pickling solution may include: water and hydrofluoric acid. Among them, the proportion of water is 90% to 95%, for example, 90%, 92%, 94%, 95%, etc.; the proportion of hydrochloric acid is 5% to 10%, for example, 5%, 7%, 8%, 10%, etc. It should be noted here that the above proportions can be expressed as volume proportions.
[0060] Preferably, the volume ratio of water to hydrofluoric acid is 420 L:40 L. Of course, other ratios are also possible and are not specifically limited here.
[0061] Optionally, the three washing times are 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.
[0062] Optionally, the time of the slow pulling and dehydration treatment is 20s to 60s, for example, 20s, 40s, 50s, 60s, etc.; the temperature of the slow pulling and dehydration treatment is 15℃ to 30℃, for example, 15℃, 20℃, 25℃, 30℃, etc.
[0063] Specifically, the eighth base silicon wafer is placed in a slow-lift tank, and a mechanical arm is provided on the slow-lift tank. The mechanical arm and the slow-lift tank cooperate to clean the water stains on the surface of the eighth base silicon wafer; the slow-lift tank and the mechanical arm clean the eighth base silicon wafer for 20s to 60s, and the temperature is 15°C to 30°C. After dehydration, the ninth base silicon wafer is obtained. It should be noted here that the specific principles and steps of the slow-lift dehydration treatment can refer to the relevant technology, which will not be elaborated here.
[0064] Optionally, the drying temperature is 80°C to 100°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the drying time is 600s to 1200s, for example, 600°C, 800°C, 1000°C, 1200°C, etc.
[0065] Specifically, the ninth base silicon wafer is placed in a drying tank for drying to remove water stains on the surface of the ninth base silicon wafer.
[0066] The present application also discloses a large and small stacked tower base silicon wafer, referring to Figure 2 and Figure 3 The disclosed large and small stacked tower base silicon wafers are made using the above-mentioned method for preparing large and small stacked tower base silicon wafers.
[0067] The embodiment of the present application also discloses a solar cell, which is made by using the above-mentioned large and small stacked tower base silicon wafers.
[0068] In summary, the embodiment of the present application improves the tower base structure of the silicon wafer to form large and small stacked tower bases with excellent interfaces, which is beneficial to the growth of polysilicon, so as to facilitate the preparation of PN junctions with better performance, which is beneficial to improving the conversion efficiency of solar cells; through the large and small stacked tower base structures, the contact area between the silicon wafer and the slurry can be increased, the contact interface between the silicon wafer and the slurry can be improved, and the contact resistance can be reduced, which is beneficial to improving the performance of solar cells; by optimizing the cleaning process, each step has clear time and temperature control, so that impurities and damage on the surface of the silicon wafer can be more thoroughly removed, which is beneficial to improving the quality, performance and service life of the silicon wafer and reducing the defect density; by optimizing the alkali polishing process, the alkali polishing process time can also be shortened, the production efficiency can be improved, and the production cost can be reduced.
[0069] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.
Claims
1. A back contact solar cell, comprising a silicon wafer as a substrate, characterized in that: A plurality of tower bases are arranged on the back side of the silicon wafer, and the plurality of tower bases are of different sizes and are stacked on each other.
2. The back contact solar cell according to claim 1, wherein: The plurality of tower bases are obtained by the following preparation method: Pre-alkaline washing: using a cleaning solution to clean the original silicon wafer to obtain a first base silicon wafer; Pre-alkali polishing: using a first alkali polishing solution to perform a first alkali polishing treatment on the first base silicon wafer to obtain a second base silicon wafer; One water washing: washing the second base silicon wafer with deionized water to obtain a third base silicon wafer; Post-alkali polishing: performing a second alkali polishing treatment on the third base silicon wafer using a second alkali polishing solution to obtain a fourth base silicon wafer; Secondary water washing: washing the fourth base silicon wafer with deionized water to obtain a fifth base silicon wafer; Ozone cleaning: cleaning the fifth base silicon wafer with ozone liquid to obtain a sixth base silicon wafer; Pickling: pickling the sixth base silicon wafer with a pickling solution to obtain a seventh base silicon wafer; Three water washings: washing the seventh base silicon wafer with deionized water to obtain an eighth base silicon wafer; Dehydration treatment: performing a slow pulling dehydration treatment on the eighth base silicon wafer to obtain a ninth base silicon wafer; Drying: Dry the ninth base silicon wafer to obtain large and small stacked tower base silicon wafers.
3. A method for preparing a back contact solar cell, comprising: A plurality of tower bases of different sizes and stacked on each other are prepared on the back of the silicon wafer.
4. The preparation method according to claim 3, wherein The step of preparing a plurality of tower bases of different sizes and stacked on each other comprises: Pre-alkaline washing: using a cleaning solution to clean the original silicon wafer to obtain a first base silicon wafer; Pre-alkali polishing: using a first alkali polishing solution to perform a first alkali polishing treatment on the first base silicon wafer to obtain a second base silicon wafer; One water washing: washing the second base silicon wafer with deionized water to obtain a third base silicon wafer; Post-alkali polishing: performing a second alkali polishing treatment on the third base silicon wafer using a second alkali polishing solution to obtain a fourth base silicon wafer; Secondary water washing: washing the fourth base silicon wafer with deionized water to obtain a fifth base silicon wafer; Ozone cleaning: cleaning the fifth base silicon wafer with ozone liquid to obtain a sixth base silicon wafer; Pickling: pickling the sixth base silicon wafer with a pickling solution to obtain a seventh base silicon wafer; Three water washings: washing the seventh base silicon wafer with deionized water to obtain an eighth base silicon wafer; Dehydration treatment: performing a slow pulling dehydration treatment on the eighth base silicon wafer to obtain a ninth base silicon wafer; Drying: Dry the ninth base silicon wafer to obtain large and small stacked tower base silicon wafers.
5. The preparation method according to claim 4, characterized in that: The pre-alkali washing comprises: The time for cleaning the original silicon wafer with the cleaning solution is 50s to 200s, and the temperature of the cleaning solution is 40°C to 70°C.
6. The preparation method according to claim 4 or 5, characterized in that: The cleaning solution comprises water, sodium hydroxide and hydrogen peroxide, wherein the water accounts for 90% to 98%, the sodium hydroxide accounts for 0.5% to 2%, and the hydrogen peroxide accounts for 2% to 8%.
7. The preparation method according to claim 4, characterized in that: The time of the first alkali polishing treatment is 180s to 200s, and the temperature of the first alkali polishing solution is 75°C to 80°C.
8. The preparation method according to claim 4 or 7, characterized in that: The components of the first alkaline polishing solution include water, sodium hydroxide and additives, wherein the water accounts for 90% to 95%, the sodium hydroxide accounts for 4% to 8%, and the additive accounts for 0.5% to 1.5%.
9. The preparation method according to claim 8, characterized in that: The time of the first washing is 60s to 200s; And / or, the secondary washing time is 60s to 200s; And / or, the three washing times are 60s to 200s.
10. The preparation method according to claim 4, characterized in that: The time of the second alkali polishing treatment is 80s to 120s, and the temperature of the second alkali polishing solution is 78°C to 84°C.
11. The preparation method according to claim 4 or 10, characterized in that: The components of the second alkaline polishing solution include water, sodium hydroxide and additives, wherein the water accounts for 80% to 85%, the sodium hydroxide accounts for 14% to 18%, and the additive accounts for 0.8% to 1.2%.
12. The preparation method according to claim 4, characterized in that: The ozone cleaning time is 200s to 800s; And / or, the components of the ozone liquid include water, ozone and hydrochloric acid, wherein the water accounts for 99.8% to 99.95%, the hydrochloric acid accounts for 0.05% to 0.2%, and the concentration of ozone is 20 ppm to 60 ppm.
13. The preparation method according to claim 4, characterized in that: The pickling time is 100s to 250s; And / or, the components of the pickling solution include water and hydrofluoric acid, wherein the water accounts for 90% to 95% and the hydrofluoric acid accounts for 5% to 10%.
14. The preparation method according to claim 4, characterized in that: The time of the slow pulling and dehydration treatment is 20s to 60s, and the temperature of the slow pulling and dehydration treatment is 15°C to 30°C.
15. The preparation method according to claim 4, characterized in that: The drying temperature is 80° C. to 100° C., and the drying time is 600s to 1200s.