TOPCon solar cell and preparation method thereof

Abstract

The invention provides a TOPCon solar cell and a preparation method thereof, and relates to the technical field of cells, a sample is oxidized before aluminum oxide is deposited on the front side of a silicon wafer, so that silicon oxide layers with high quality are formed on the surface of a doped polycrystalline silicon layer and the surface of a boron-doped monocrystalline silicon layer; the aluminum oxide negative charge density and the silicon-hydrogen bond concentration on the surface of the TOPCon solar cell are increased, so that the stability of an aluminum oxide and silicon nitride laminated layer on the light receiving surface of the TOPCon solar cell under ultraviolet irradiation is improved, and the purpose of reducing ultraviolet induced degradation of the TOPCon cell is achieved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a TOPCon solar cell and a preparation method thereof. Background Art

[0002] TOPCon (Tunnel Oxide Passivation Contact) solar cells are tunnel oxide passivation contact solar cells with silicon as substrate. They deposit tunnel oxide and doped polysilicon layer on the back of silicon wafers to effectively reduce surface recombination and metal contact recombination, improve opening voltage and energy conversion efficiency, and achieve good passivation effect. They are currently in large-scale mass production on the market. Studies have shown that the current TOPCon cells are facing UVID (Ultraviolet Induced Degradation) problems. The main reason for the UVID problem is that ultraviolet radiation will destroy the Si-H bonds in the cell structure and increase interface state defects, thereby reducing the cell interface passivation performance and cell efficiency attenuation.

[0003] At present, the industry mainly reduces the UVID phenomenon on TOPCon cells by improving battery materials, packaging technology, optimizing battery structure, etc., but the effect of improving battery materials and packaging technology on suppressing the UVID problem is not good. In terms of optimizing battery structure, the existing technology improves the anti-UVID effect of the battery by introducing aluminum oxide into the battery structure. Although this technical means has alleviated the UVID problem of TOPCon solar cells to a certain extent, it is still necessary to further reduce the ultraviolet induced attenuation of TOPCon solar cells. Summary of the invention

[0004] The problem solved by the present invention is: how to further reduce the ultraviolet induced attenuation of the TOPCon solar cell.

[0005] In order to solve the above problems, the present invention provides a method for preparing a TOPCon solar cell, comprising:

[0006] Step S1, after pre-treating the silicon wafer, performing boron diffusion on the front side of the silicon wafer to form a boron-doped single-crystalline silicon layer, and sequentially preparing a tunneling oxide layer and a doped polysilicon layer on the back side of the silicon wafer to obtain a first intermediate sample;

[0007] Step S2, performing oxidation treatment on the first intermediate sample to form a first silicon oxide layer on the surface of the doped polysilicon layer and a second silicon oxide layer on the surface of the boron-doped single crystal silicon layer, to obtain a second intermediate sample; wherein the thickness of the first silicon oxide layer and the second silicon oxide layer are both 0.5-2.5 nm;

[0008] Step S3, sequentially depositing a first aluminum oxide layer and a first silicon nitride layer on the surface of the first silicon oxide layer, and sequentially depositing a second aluminum oxide layer and a second silicon nitride layer on the surface of the second silicon oxide layer to obtain a third intermediate sample;

[0009] Step S4: After preparing the electrode on the third intermediate sample, sintering treatment and light injection treatment are performed in sequence to obtain a TOPCon solar cell.

[0010] Optionally, in S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an ozone atmosphere; wherein the heating treatment temperature is 200-300°C.

[0011] Optionally, in S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an oxygen atmosphere; wherein the heating treatment temperature is 300-600°C.

[0012] Optionally, in S3, the thickness of the first aluminum oxide layer and the second aluminum oxide layer are both 2-10 nm.

[0013] Optionally, in S3, the thickness of the first silicon nitride layer and the second silicon nitride layer are both 70-90 nm.

[0014] Optionally, in step S1, the pre-processing of the silicon wafer includes: cleaning the silicon wafer and then texturing both sides of the silicon wafer.

[0015] Optionally, in step S4, the sintering temperature is 700-750°C.

[0016] Optionally, in step S4, the temperature of the light injection treatment is 200-700°C.

[0017] Optionally, in step S1, the tunneling oxide layer is made of silicon dioxide.

[0018] The present invention also provides a TOPCon solar cell, which is manufactured using the above-mentioned method for manufacturing the TOPCon solar cell.

[0019] Compared with the prior art, the present invention performs oxidation treatment on the sample before depositing aluminum oxide on the front side of the silicon wafer, thereby forming a high-quality silicon oxide layer on the surface of the doped polysilicon layer and the surface of the boron-doped single-crystal silicon layer, which is beneficial to increase the negative charge density of aluminum oxide and the concentration of silicon-hydrogen bonds on the surface of the TOPCon solar cell, thereby improving the stability of the aluminum oxide and silicon nitride stack on the light-receiving surface of the TOPCon solar cell under ultraviolet irradiation, and achieving the purpose of reducing the ultraviolet induced attenuation of the TOPCon solar cell. In addition, the introduction of the silicon oxide layer also helps to reduce the surface energy of the TOPCon solar cell, improve the carrier mobility, and improve the photoelectric performance of the TOPCon solar cell. The introduction of the silicon oxide layer also helps to reduce the impact of pollutants on the silicon surface in subsequent processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process for preparing a TOPCon solar cell according to an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the structure of a TOPCon solar cell in an embodiment of the present invention;

[0022] Figure 3 This is a comparison diagram of the interface state density of the TOPCon solar cells prepared in Example 1 and Comparative Example 1 after UV15 irradiation;

[0023] Figure 4 This is a comparison diagram of negative fixed charges of the TOPCon solar cells prepared in Example 1 and Comparative Example 1 after UV15 irradiation.

[0024] Description of reference numerals:

[0025] 1. Silicon wafer; 2. Boron-doped single crystal silicon layer; 3. Tunneling oxide layer; 4. Doped polysilicon layer; 5. First silicon oxide layer; 6. Second silicon oxide layer; 7. First aluminum oxide layer; 8. First silicon nitride layer; 9. Second aluminum oxide layer; 10. Second silicon nitride layer. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application;

[0028] The term "including" and its variations used in this article are open inclusions, that is, "including but not limited to"; the term "based on" is "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, the meaning of "multiple" is two or more.

[0029] Research has found that after aluminum oxide is prepared on the front of the TOPCon solar cell, a silicon oxide layer will naturally form between the aluminum oxide and silicon, and its thickness is usually 1-1.2nm. The quality of the silicon oxide layer determines the negative charge density of aluminum oxide on the surface of the TOPCon solar cell. When the negative charge density of aluminum oxide on the surface of the TOPCon solar cell is larger, the passivation effect is better and the anti-ultraviolet radiation performance is better.

[0030] Based on the above considerations, if Figure 1 As shown, a method for preparing a TOPCon solar cell provided by an embodiment of the present invention includes:

[0031] Step S1, after pre-treating the silicon wafer 1, performing boron diffusion on the front side of the silicon wafer 1 to form a boron-doped single crystal silicon layer 2, and sequentially preparing a tunneling oxide layer 3 and a doped polysilicon layer 4 on the back side of the silicon wafer 1 to obtain a first intermediate sample;

[0032] Step S2, performing oxidation treatment on the first intermediate sample to form a first silicon oxide layer 5 on the surface of the doped polysilicon layer 4 and a second silicon oxide layer 6 on the surface of the boron-doped single crystal silicon layer 2, to obtain a second intermediate sample; wherein the thickness of the first silicon oxide layer 5 and the second silicon oxide layer 6 are both 0.5-2.5 nm;

[0033] Step S3, depositing a first aluminum oxide layer 7 and a first silicon nitride layer 8 on the surface of the first silicon oxide layer 5 in sequence, and depositing a second aluminum oxide layer 9 and a second silicon nitride layer 10 on the surface of the second silicon oxide layer 6 in sequence, to obtain a third intermediate sample;

[0034] Step S4: After preparing the electrode on the third intermediate sample, sintering treatment and light injection treatment are performed in sequence to obtain a TOPCon solar cell, such as Figure 2 shown.

[0035] In the embodiment of the present invention, the sample is oxidized before aluminum oxide is deposited on the front side of the silicon wafer 1, thereby forming a high-quality silicon oxide layer on the surface of the doped polycrystalline silicon layer and the surface of the boron-doped single crystal silicon layer 2, which is beneficial to increase the negative charge density of aluminum oxide and the silicon-hydrogen bond concentration on the surface of the TOPCon solar cell, thereby improving the stability of the aluminum oxide and silicon nitride stack on the light-receiving surface of the TOPCon solar cell under ultraviolet irradiation, thereby achieving the purpose of reducing the ultraviolet induced attenuation of the TOPCon cell.

[0036] In some embodiments of the present invention, the thickness of the first silicon oxide layer 5 and the second silicon oxide layer 6 are both 1.0-2.0 nm.

[0037] In some embodiments of the present invention, in S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an ozone atmosphere; wherein the heating treatment temperature is 200-300°C.

[0038] In some embodiments of the present invention, in S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an oxygen atmosphere; wherein the heating treatment temperature is 300-600°C.

[0039] In some embodiments of the present invention, in S3, the thickness of the first aluminum oxide layer 7 and the second aluminum oxide layer 9 are both 2-10 nm. Preferably, the thickness of the first aluminum oxide layer 7 and the second aluminum oxide layer 9 are both 10 nm. When the thickness of the first aluminum oxide layer 7 and the second aluminum oxide layer 9 is larger, the ultraviolet induced attenuation of the efficiency of the TOPCon solar cell can be further reduced.

[0040] In some embodiments of the present invention, in S3, the thickness of the first silicon nitride layer 8 and the second silicon nitride layer 10 are both 70-90 nm.

[0041] In some embodiments of the present invention, in step S1, the pre-treatment of the silicon wafer 1 includes: cleaning the silicon wafer 1 and then texturing the double sides of the silicon wafer 1.

[0042] In some embodiments of the present invention, in step S4, the temperature of the sintering treatment is 700-750°C.

[0043] In some embodiments of the present invention, in step S4, the temperature of the light injection treatment is 200-700°C.

[0044] In some embodiments of the present invention, in step S1 , the tunnel oxide layer 3 is made of silicon dioxide.

[0045] In some embodiments of the present invention, in step S3, before depositing the first aluminum oxide layer and the second aluminum oxide layer, the deposition chamber is purged with nitrogen for 40 seconds, which is beneficial to further improve the efficiency of the TOPCon solar cell under the condition of ultraviolet induced attenuation that reduces the efficiency of the TOPCon solar cell.

[0046] The present invention also provides a TOPCon solar cell, which is manufactured using the above-mentioned method for manufacturing the TOPCon solar cell.

[0047] The present invention is further described below in conjunction with specific embodiments.

[0048] Example 1

[0049] A1. After cleaning the N-type silicon wafer, double-sided texturing is performed, and then boron is diffused on the front side of the N-type silicon wafer to form a boron-doped single-crystalline silicon layer. The boron-doped single-crystalline silicon layer and the N-type silicon wafer form a PN junction; wherein the thickness of the N-type silicon wafer is 130μm.

[0050] A2. Silicon dioxide and phosphorus-doped amorphous silicon are sequentially deposited on the back side of an N-type silicon wafer, and annealed to convert the phosphorus-doped amorphous silicon into phosphorus-doped polysilicon. The silicon dioxide and phosphorus-doped polysilicon coated on the front side of the N-type silicon wafer are removed, thereby obtaining a tunneling oxide layer (made of silicon dioxide) and a phosphorus-doped polysilicon layer on the back side of the N-type silicon wafer to obtain a first intermediate sample; wherein the thickness of the tunneling oxide layer is 1.5 nm, and the thickness of the phosphorus-doped polysilicon layer is 120 nm.

[0051] A3. Heat-treat the first intermediate sample in an ozone atmosphere to form a first silicon oxide layer on the surface of the doped polysilicon layer and a second silicon oxide layer on the surface of the boron-doped single crystal silicon layer, so as to obtain a second intermediate sample; wherein the heat treatment temperature is 260°C, and the thickness of the first silicon oxide layer and the second silicon oxide layer are both 1.5 nm.

[0052] A4. Al2O3 and silicon nitride are sequentially deposited on the surface of the first silicon oxide layer to form a first aluminum oxide layer and a first silicon nitride layer. Al2O3 and silicon nitride are sequentially deposited on the surface of the second silicon oxide layer to form a second aluminum oxide layer and a second silicon nitride layer to obtain a third intermediate sample; wherein the thickness of the first aluminum oxide layer is 5nm, the thickness of the second aluminum oxide layer is 5nm, and the thickness of the first silicon nitride layer and the second silicon nitride layer are both 80nm.

[0053] A5. After preparing the electrode on the third intermediate sample by screen printing, sintering treatment and light injection treatment are carried out in sequence to obtain a TOPCon solar cell; wherein the sintering treatment temperature is 720°C, and the light injection treatment temperature is 550°C.

[0054] Example 2

[0055] The difference from Example 1 is that in step A3, the temperature of the heating treatment is 300° C., and the thickness of the first silicon oxide layer and the second silicon oxide layer are both 2 nm.

[0056] Example 3

[0057] The difference from Example 1 is that in step A3, the temperature of the heating treatment is 200° C., and the thickness of the first silicon oxide layer and the second silicon oxide layer are both 1.0 nm.

[0058] Example 4

[0059] The difference from Example 1 is that step A3 is: heat-treating the first intermediate sample in an oxygen atmosphere to form a first silicon oxide layer on the surface of the doped polysilicon layer and a second silicon oxide layer on the surface of the boron-doped single crystal silicon layer, thereby obtaining a second intermediate sample; wherein the temperature of the heat treatment is 600°C, and the thickness of the first silicon oxide layer and the second silicon oxide layer are both 1.8 nm. In step A4, the thickness of the first aluminum oxide layer is 10 nm, and the thickness of the second aluminum oxide layer is 10 nm.

[0060] Example 5

[0061] The difference from Example 1 is that step A3 is: heat-treating the first intermediate sample in an oxygen atmosphere to form a first silicon oxide layer on the surface of the doped polysilicon layer and a second silicon oxide layer on the surface of the boron-doped single crystal silicon layer, to obtain a second intermediate sample; wherein the temperature of the heat treatment is 500°C, and the thickness of the first silicon oxide layer and the second silicon oxide layer are both 1.6nm. In step A4, the thickness of the first aluminum oxide layer is 10nm, and the thickness of the second aluminum oxide layer is 10nm.

[0062] Example 6

[0063] The difference from Example 5 is that before depositing the first aluminum oxide layer and the second aluminum oxide layer, the deposition chamber is purged with nitrogen for 40 seconds.

[0064] Comparative Example 1

[0065] B1. After cleaning the N-type silicon wafer, double-sided texturing is performed, and then boron is diffused on the front side of the N-type silicon wafer to form a boron-doped single-crystalline silicon layer. The boron-doped single-crystalline silicon layer and the N-type silicon wafer form a PN junction; wherein the thickness of the N-type silicon wafer is 130 μm.

[0066] B2. Silicon dioxide and phosphorus-doped amorphous silicon are sequentially deposited on the back side of an N-type silicon wafer, and annealed to convert the phosphorus-doped amorphous silicon into phosphorus-doped polysilicon. The silicon dioxide and phosphorus-doped polysilicon coated on the front side of the N-type silicon wafer are removed, thereby obtaining a tunneling oxide layer (made of silicon dioxide) and a phosphorus-doped polysilicon layer on the back side of the N-type silicon wafer to obtain a first intermediate sample; wherein the thickness of the tunneling oxide layer is 1.5 nm, and the thickness of the phosphorus-doped polysilicon layer is 120 nm.

[0067] B3. Al2O3 and silicon nitride are sequentially deposited on the surface of the phosphorus-doped polysilicon layer to form a first aluminum oxide layer and a first silicon nitride layer, and Al2O3 and silicon nitride are sequentially deposited on the surface of the boron-doped single crystal silicon layer to form a second aluminum oxide layer and a second silicon nitride layer, to obtain a second intermediate sample; wherein the thickness of the first aluminum oxide layer is 5nm, the thickness of the second aluminum oxide layer is 5nm, and the thickness of the first silicon nitride layer and the second silicon nitride layer are 80nm.

[0068] B4. After preparing the electrode on the second intermediate sample by screen printing, sintering treatment and light injection treatment are carried out in sequence to obtain a TOPCon solar cell; wherein the sintering treatment temperature is 720°C, and the light injection treatment temperature is 550°C.

[0069] Comparative Example 2

[0070] The difference from Comparative Example 1 is that in step B3, the thickness of the first aluminum oxide layer is 10 nm, and the thickness of the second aluminum oxide layer is 10 nm.

[0071] Experimental example

[0072] The interface state density (dit) and negative fixed charge (Q) of the TOPCon solar cells prepared in Example 1 and Comparative Example 1 after UV15 irradiation were compared. f ) for testing, the results are shown in Figure 3 and Figure 4 ,from Figure 3 and Figure 4 It can be seen that compared with Comparative Example 1, the interface state density (dit) of the TOPCon solar cell prepared in Example 1 after UV15 irradiation is lower, and the negative fixed charge (Qf ) is more, indicating better passivation effect and better anti-ultraviolet radiation performance.

[0073] It should be noted that UV15 irradiation refers to the TOPCon solar cell at 15KWh / m 2 irradiated under ultraviolet light. Figure 3 and Figure 4 “Not oxidized” corresponds to the data of Example 1, and “oxidized” corresponds to the data of Example 1.

[0074] The TOPCon solar cells prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to performance tests and UV attenuation tests, and the results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1-2, the efficiency attenuation of the TOPCon solar cells prepared in Examples 1-6 is smaller under UV irradiation, indicating that the UV-induced attenuation of the efficiency of the TOPCon solar cells prepared in Examples 1-6 is smaller; compared with Comparative Example 1, the UV-induced attenuation of the efficiency of the TOPCon solar cells prepared in Comparative Example 2 is smaller, indicating that when the thickness of the Al2O3 layer is larger, the UV-induced attenuation of the efficiency of the TOPCon solar cells can be further reduced. Compared with Example 5, the efficiency of the TOPCon solar cells prepared in Example 6 is higher, indicating that before depositing the first aluminum oxide layer and the second aluminum oxide layer, nitrogen is purged in the deposition chamber for 40 seconds, which is beneficial to further improve the efficiency of the TOPCon solar cells while reducing the UV-induced attenuation of the efficiency of the TOPCon solar cells.

[0075] It should be noted that in Table 1, UV60 efficiency degradation refers to the TOPCon solar cell at 60KWh / m 2 The efficiency decay under ultraviolet light, V oc is the open circuit voltage of the TOPCon solar cell, I sc is the short-circuit current of the TOPCon solar cell, and η is the efficiency of the TOPCon solar cell.

[0076] Table 1

[0077]

[0078] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that: include: Step S1, after pre-treating the silicon wafer (1), performing boron diffusion on the front side of the silicon wafer (1) to form a boron-doped single-crystalline silicon layer (2), and sequentially preparing a tunneling oxide layer (3) and a doped polysilicon layer (4) on the back side of the silicon wafer (1) to obtain a first intermediate sample; Step S2, performing an oxidation treatment on the first intermediate sample to form a first silicon oxide layer (5) on the surface of the doped polysilicon layer (4), and a second silicon oxide layer (6) on the surface of the boron-doped single crystal silicon layer (2), to obtain a second intermediate sample; wherein the thickness of the first silicon oxide layer (5) and the second silicon oxide layer (6) are both 0.5-2.5 nm; Step S3, depositing a first aluminum oxide layer (7) and a first silicon nitride layer (8) on the surface of the first silicon oxide layer (5) in sequence, and depositing a second aluminum oxide layer (9) and a second silicon nitride layer (10) on the surface of the second silicon oxide layer (6) in sequence, to obtain a third intermediate sample; Step S4: After preparing the electrode on the third intermediate sample, sintering treatment and light injection treatment are performed in sequence to obtain a TOPCon solar cell.

2. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an ozone atmosphere; wherein the heating treatment temperature is 200-300°C.

3. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In S2, the oxidation treatment of the first intermediate sample includes: heating the first intermediate sample in an oxygen atmosphere; wherein the heating treatment temperature is 300-600°C.

4. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In S3, the thickness of the first aluminum oxide layer (7) and the second aluminum oxide layer (9) are both 2-10 nm.

5. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In S3, the thickness of the first silicon nitride layer (8) and the second silicon nitride layer (10) are both 70-90 nm.

6. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In the step S1, the pretreatment of the silicon wafer (1) comprises: cleaning the silicon wafer (1) and then texturing both sides of the silicon wafer (1).

7. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In the step S4, the temperature of the sintering treatment is 700-750°C.

8. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In the step S4, the temperature of the light injection treatment is 200-700°C.

9. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In the step S1, the material of the tunnel oxide layer (3) is silicon dioxide.

10. A TOPCon solar cell, characterized in that: The TOPCon solar cell is prepared by the preparation method of any one of claims 1 to 9.

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