Back contact solar cell with double-passivation structure and preparation method of back contact solar cell

Abstract

The invention relates to the technical field of back contact solar cells, in particular to a back contact solar cell with a double-passivation structure and a preparation method thereof, and the front surface of the cell sequentially comprises an antireflection film, a suede structure and an N-type monocrystalline silicon wafer from outside to inside; a back field region on the back surface of the back contact solar cell sequentially comprises a metal electrode, an antireflection film, a second phosphorus-doped polycrystalline silicon layer, a second tunneling oxide layer, a first phosphorus-doped polycrystalline silicon layer, a first tunneling oxide layer and an N-type monocrystalline silicon wafer from outside to inside; the emitter region sequentially comprises a metal electrode, an antireflection film, a transparent conductive film, a boron-doped amorphous silicon layer, an intrinsic amorphous silicon layer and an N-type monocrystalline silicon wafer from outside to inside; the isolation area sequentially comprises an antireflection film, a suede structure and an N-type monocrystalline silicon wafer from outside to inside. A P-type TOPCon structure of an emitter region of the TBC battery is optimized into an intrinsic amorphous silicon + P-type amorphous silicon passivation structure with better passivation performance and contact performance, and the conversion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of back-contact solar cells, and particularly to a back-contact solar cell with a double-passivation structure and a preparation method thereof. Background Art

[0002] TBC cells (Tunneling Oxide Passivated Contact Back Contact) are widely used due to their good passivation effect. However, TBC cells have problems of poor passivation performance and metal contact performance of the back emitter (P-type polysilicon), which further limits the further improvement of the conversion efficiency of back-contact cells. Summary of the Invention

[0003] The purpose of the present invention is to provide a back-contact solar cell with a double-passivation structure and a preparation method thereof to solve the above technical problems.

[0004] To achieve the above purpose, the present invention provides a back-contact solar cell with a double-passivation structure. The front side of the back-contact solar cell sequentially includes, from outside to inside: an antireflection film 502, a textured structure 501, and an N-type monocrystalline silicon wafer 101; the back side of the back-contact solar cell is divided into a back field region 10, an emitter region 20, and an isolation region 30 between the back field region and the emitter region; the back field region 10 sequentially includes, from outside to inside: a metal electrode 601, an antireflection film 502, a second phosphorus-doped polysilicon layer 202', a second tunneling oxide layer 201', a first phosphorus-doped polysilicon layer 202, a first tunneling oxide layer 201, and an N-type monocrystalline silicon wafer 101; the emitter region 20 sequentially includes, from outside to inside: a metal electrode 601, an antireflection film 502, a transparent conductive thin film 303, a boron-doped amorphous silicon layer 302, an intrinsic amorphous silicon layer 301, and an N-type monocrystalline silicon wafer 101; the isolation region 30 sequentially includes, from outside to inside: an antireflection film 502, a textured structure 501, and an N-type monocrystalline silicon wafer 101.

[0005] The present invention also provides a preparation method of a back-contact solar cell with a double-passivation structure. The method includes:

[0006] Sequentially depositing a first tunneling oxide layer 201, a first phosphorus-doped polysilicon layer 202, a second tunneling oxide layer 201', a second phosphorus-doped polysilicon layer 202', and a mask layer 203 on one side of the N-type monocrystalline silicon wafer 101;

[0007] Forming a back field region 10 and a non-back field region by opening the film on the mask layer 203, and polishing and cleaning them;

[0008] Sequentially depositing an intrinsic amorphous silicon layer 301, a boron-doped amorphous silicon layer 302, and a transparent conductive thin film 303 on the cleaned back field region 10 and non-back field region;

[0009] An initial semi-finished product is obtained after printing a protective paste 401 on a transparent conductive thin film 303 in a non-back-field region;

[0010] After cleaning and texturing the initial semi-finished product, the non-back-field region is divided into isolation regions 30 and emitter regions 20, and a semi-finished product is obtained after forming a textured structure 501 on the other side of the isolation regions and the N-type monocrystalline silicon wafer 101;

[0011] An antireflection film 502 is deposited on both sides of the semi-finished product, and metal electrodes 601 are prepared in the emitter region and the back-field region to obtain a back-contact solar cell with a double-passivation structure.

[0012] Technical effects and advantages of the present invention:

[0013] The present invention optimizes the P-type TOPCon structure in the emitter region of the TBC cell into an intrinsic amorphous silicon + P-type amorphous silicon passivation structure with better passivation performance and contact performance, greatly improving the conversion efficiency of the back-contact cell. Compared with the process flow of the TBC cell using the P-type TOPCon structure, the process steps are not increased but rather simplified.

[0014] Other features and advantages of the present invention will be described in the subsequent specification, and, in part, will be obvious from the specification or will be understood by implementing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a structural diagram of a back-contact solar cell with a double-passivation structure;

[0017] Figure 2 It is a schematic diagram of depositing a double-layer tunneling oxide layer, a phosphorus-doped polysilicon (n-poly) layer, and a mask layer;

[0018] Figure 3 It is a schematic diagram of laser grooving, polishing, and cleaning;

[0019] Figure 4 It is a schematic diagram of depositing an intrinsic amorphous silicon (i-a-Si) layer and a boron-doped amorphous silicon (p-a-Si) layer;

[0020] Figure 5 It is a schematic diagram of printing a protective paste;

[0021] Figure 6 It is a schematic diagram of cleaning and texturing;

[0022] Figure 7 It is a schematic diagram of double-sided deposition of antireflection film;

[0023] Reference numerals: N-type monocrystalline silicon wafer - 101, first tunneling oxide layer - 201, first phosphorus-doped polysilicon layer - 202, second tunneling oxide layer - 201', second phosphorus-doped polysilicon layer - 202', mask layer - 203, intrinsic amorphous silicon layer - 301, boron-doped amorphous silicon layer - 302, transparent conductive thin film - 303, protective paste - 401, textured structure - 501, antireflection film - 502, metal electrode - 601, back field region - 10, emitter region - 20, isolation region - 30. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have technical substantial significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear narration and are not used to limit the scope under which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope under which the present invention can be implemented.

[0026] To better understand the present invention, the overall concept of the present invention is introduced as follows:

[0027] The present invention is to deposit a first tunneling oxide layer 201, a first phosphorus-doped polysilicon layer 202, a second tunneling oxide layer 201', a second phosphorus-doped polysilicon layer 202' and a mask layer 203 on a polished N-type monocrystalline silicon wafer through a single process of a PECVD device. Then, a back field region 10 and an emitter region 20 are prepared by patterning, and then polished and cleaned. Then, an intrinsic amorphous silicon layer (i-a-Si) 301, a boron-doped amorphous silicon layer (p-a-Si) 302 and a transparent conductive thin film (TCO) 303 are deposited on the emitter region 20 at one time using a PVD device. A protective paste 401 is locally printed on the transparent conductive thin film (TCO) 303 to protect the underlying TCO, p-a-Si and i-a-Si, and then cleaned and textured to form a textured structure on the back isolation region 30 and the front side of the cell. Finally, a double-sided antireflection film (such as a silicon nitride antireflection layer) is deposited, and positive and negative electrodes are printed to fabricate a back contact cell with a double passivation structure.

[0028] The following is a detailed introduction to the present invention. The present invention provides a back contact solar cell with a double passivation structure, and this structure is as Figure 1 shown.

[0029] The front side of the back contact solar cell sequentially includes, from outside to inside: an antireflection film 502, a textured structure 501 and an N-type monocrystalline silicon wafer 101; the back side of the back contact solar cell is divided into a back field region 10, an emitter region 20, and an isolation region 30 between the back field region and the emitter region; the back field region sequentially includes, from outside to inside: a metal electrode 601, an antireflection film 502, a second phosphorus-doped polysilicon layer 202', a second tunneling oxide layer 201', a first phosphorus-doped polysilicon layer 202, a first tunneling oxide layer 201, and an N-type monocrystalline silicon wafer 101; the emitter region sequentially includes, from outside to inside: a metal electrode 601, an antireflection film 502, a transparent conductive thin film 303, a boron-doped amorphous silicon layer 302, an intrinsic amorphous silicon layer 301, and an N-type monocrystalline silicon wafer 101; the isolation region sequentially includes, from outside to inside: an antireflection film 502, a textured structure 501 and an N-type monocrystalline silicon wafer 101.

[0030] The present invention also provides a method for manufacturing a back contact solar cell with a double passivation structure, which specifically includes:

[0031] S1. Select an N-type monocrystalline silicon wafer 101 as the substrate and perform surface damage removal treatment.

[0032] Among them, the thickness of the N-type monocrystalline silicon wafer is 50 - 300 μm, preferably 100 - 200 μm, more preferably 100 - 140 μm, the resistivity is 0.1 - 50 Ω·cm, preferably 1 - 41 Ω·cm, more preferably 3 - 25 Ω·cm.

[0033] S2. Use a PECVD device to deposit the first tunneling oxide layer 201, the first phosphorus-doped polysilicon layer 202, the second tunneling oxide layer 201', the second phosphorus-doped polysilicon layer 202', and the mask layer 203 on the back of the battery in one step, as Figure 2 shown.

[0034] Among them, the thickness of the first tunneling oxide layer is 0.1 - 5 nm, preferably 1 - 2.5 nm, and more preferably 1.4 - 2.2 nm.

[0035] Among them, the thickness of the first phosphorus-doped polysilicon layer is 10 - 50 nm, preferably 16 - 42 nm, and more preferably 24 - 36 nm, and the surface doping concentration is 1×10 20 cm -3 -5×10 20 cm -3 , and theoretically, the higher the better.

[0036] Among them, the thickness of the second tunneling oxide layer is 0.1 - 5 nm, preferably 1 - 2.5 nm, and more preferably 1.4 - 2.2 nm.

[0037] Among them, the thickness of the second phosphorus-doped polysilicon layer is 30 - 100 nm, preferably 42 - 89 nm, and more preferably 59 - 77 nm, and the surface doping concentration is 5×10 20 cm -3 -1×10 21 cm -3 , and theoretically, the higher the better.

[0038] Among them, the mask layer material includes one or a combination of silicon dioxide / silicon oxynitride / silicon nitride film layers, but is not limited to these mask materials, and the thickness of the mask layer is 30 - 200 nm, preferably 53 - 184 nm, and more preferably 88 - 135 nm.

[0039] S3. Open the film on the battery mask layer (using the method of laser film opening or printing and etching slurry for film opening, but not limited to these two methods), the film opening width is 0 - 1000 μm, preferably 220 - 853 μm, and more preferably 450 - 750 μm, and then polish and clean the battery, as Figure 3 shown.

[0040] S4. Deposit an intrinsic amorphous silicon (i-a-Si) layer 301, a boron-doped amorphous silicon (p-a-Si) layer 302, and a transparent conductive thin film 303 on the entire back of the battery, as Figure 4 shown.

[0041] Among them, the thickness of the intrinsic amorphous silicon layer is 1 - 5 nm, preferably 1.1 - 4.5 nm, and more preferably 2.3 - 3.8 nm.

[0042] Among them, the thickness of the boron-doped amorphous silicon layer is 10-100 nm, preferably 31-89 nm, more preferably 46-72 nm, and the surface doping concentration is 1×10 19 cm -3 -5×10 20 cm -3 , and theoretically, the higher the better.

[0043] Among them, the thickness of the transparent conductive thin film is 50-100 nm, preferably 58-89 nm, more preferably 65-74 nm.

[0044] S5. Print the protective paste 401 on the transparent conductive thin film 303, as Figure 5 shown.

[0045] S6. Clean and texture the semi-finished product prepared in S5 to form a textured surface structure 501 (such as a pyramid or an inverted pyramid) on the isolation areas on the front and back of the battery, as Figure 6 shown.

[0046] S7. Deposit an antireflection film 502 on both the front and back sides of the semi-finished product prepared in S6, as Figure 7 shown.

[0047] S8. Prepare the metal electrode 601 on the antireflection film 502 in the emitter region and the back field region to prepare a back contact solar cell with a double passivation structure, as Figure 1 shown.

[0048] To better explain this solution, the following also provides examples and comparative examples.

[0049] Examples

[0050] S1. Select an N-type monocrystalline silicon wafer 101 as the substrate and perform surface damage removal treatment.

[0051] Among them, the thickness of the N-type monocrystalline silicon wafer is 140 μm, and the resistivity is 6-10 Ω·cm.

[0052] S2. Use a PECVD device to deposit the first tunneling oxide layer 201, the first phosphorus-doped polysilicon layer 202, the second tunneling oxide layer 201', the second phosphorus-doped polysilicon layer 202', and the mask layer 203 in one step on the back of the battery, as Figure 2 shown.

[0053] Among them, the thickness of the first tunneling oxide layer is 1.8 nm.

[0054] Among them, the thickness of the first phosphorus-doped polysilicon layer is 40 nm, and the surface doping concentration is 5×10 20 cm -3 .

[0055] Among them, the thickness of the second tunneling oxide layer is 2.0 nm.

[0056] Among them, the thickness of the second phosphorus-doped polysilicon layer is 90 nm, and the surface doping concentration is 8×10 20 cm -3 .

[0057] Among them, the mask layer material includes one or a combination of silicon dioxide / silicon oxynitride / silicon nitride film layers, but is not limited to these mask materials, and the thickness of the mask layer is 130 nm.

[0058] S3. Open a film on the battery mask layer (using methods such as laser film opening or printing and etching slurry for film opening, but not limited to these two), the film opening width is 650 μm, and then polish and clean the battery, as Figure 3 shown.

[0059] S4. Deposit an intrinsic amorphous silicon (i-a-Si) layer 301, a boron-doped amorphous silicon (p-a-Si) layer 302, and a transparent conductive thin film 303 on the entire back surface of the battery, as Figure 4 shown.

[0060] Among them, the thickness of the intrinsic amorphous silicon layer is 1.5 nm.

[0061] Among them, the thickness of the boron-doped amorphous silicon layer is 70 nm, and the surface doping concentration is 5×10 20 cm -3 .

[0062] Among them, the thickness of the transparent conductive thin film is 60 nm.

[0063] S5. Print a protective slurry 401 on the transparent conductive thin film 303, as Figure 5 shown.

[0064] S6. Clean and texture the semi-finished product prepared in S5 to form a pyramid (or inverted pyramid) textured surface structure 501 on the isolation areas on the front and back surfaces of the battery, as Figure 6 shown.

[0065] S7. Deposit an antireflection film 502 on both the front and back sides of the semi-finished product prepared in S6, as Figure 7 shown.

[0066] S8. Prepare a metal electrode 601 on the antireflection film 502 in the emitter region and the back field region to prepare a back contact solar cell with a double passivation structure.

[0067] Comparative example

[0068] For the preparation method of the back contact battery in the comparative example, please refer to the patent of CN114093980B.

[0069] The electrical performance comparison tests were carried out on the back-contact batteries of the example and the comparative example respectively, and the experimental results are as follows:

[0070] Open-circuit voltage Fill factor Conversion efficiency Example 745 mV 84％ 27％ Comparative example 740 mV 83.5％ 26.5％

[0071] It can be seen from the data that the back-contact battery protected by the example has obtained a higher open-circuit voltage and fill factor compared with the comparative example, and thus has a higher conversion efficiency.

[0072] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A back contact solar cell with a double passivation structure, characterized in that: The front side of the back-contact solar cell includes, from outside to inside: an anti-reflection film (502), a velvet structure (501), and an N-type single crystal silicon wafer (101); the back side of the back-contact solar cell is divided into a back field region (10), an emitter region (20), and an isolation region (30) between the back field region and the emitter region; the back field region (10) includes, from outside to inside: a metal electrode (601), an anti-reflection film (502), a second phosphorus-doped polysilicon layer (202'), a second tunneling oxide layer (201'), a first A phosphorus-doped polysilicon layer (202), a first tunneling oxide layer (201), and an N-type single crystal silicon wafer (101); the emitter region (20) comprises, from the outside to the inside: a metal electrode (601), an anti-reflection film (502), a transparent conductive film (303), a boron-doped amorphous silicon layer (302), an intrinsic amorphous silicon layer (301), and an N-type single crystal silicon wafer (101); and the isolation region (30) comprises, from the outside to the inside: an anti-reflection film (502), a velvet structure (501), and an N-type single crystal silicon wafer (101).

2. The back contact solar cell according to claim 1, characterized in that: The thickness of the N-type single crystal silicon wafer (101) is 50-300 μm, and the resistivity is 0.1-50 Ω˙cm.

3. The back contact solar cell according to claim 1, characterized in that: The thickness of the first tunnel oxide layer (201) is 0.1-5 nm.

4. The back contact solar cell according to claim 1, characterized in that: The thickness of the second tunnel oxide layer (201') is 0.1-5 nm.

5. The back contact solar cell according to claim 1, characterized in that: The first phosphorus-doped polysilicon layer (202) has a thickness of 10-50 nm, and a surface doping concentration of 1×10 20 cm -3 -5×10 20 cm -3 .

6. The back contact solar cell according to claim 1, characterized in that: The second phosphorus-doped polysilicon layer (202') has a thickness of 30-100 nm, and a surface doping concentration of 5×10 20 cm -3 -1×10 21 cm -3 .

7. The back contact solar cell according to claim 1, characterized in that: The intrinsic amorphous silicon layer (301) has a thickness of 1-5 nm; the boron-doped amorphous silicon layer (302) has a thickness of 10-100 nm, and the surface doping concentration of the boron-doped amorphous silicon layer (302) is 1×10 19 cm -3 -5×10 20 cm -3 ; The thickness of the transparent conductive film (303) is 50-100nm.

8. A method for preparing a back-contact solar cell with a double passivation structure according to any one of claims 1 to 7, characterized in that: The method comprises: A first tunneling oxide layer (201), a first phosphorus-doped polysilicon layer (202), a second tunneling oxide layer (201'), a second phosphorus-doped polysilicon layer (202') and a mask layer (203) are sequentially deposited on one side of an N-type single crystal silicon wafer (101); Forming a back field region (10) and a non-back field region on the mask layer (203) by opening the film, and polishing and cleaning them; Sequentially depositing an intrinsic amorphous silicon layer (301), a boron-doped amorphous silicon layer (302) and a transparent conductive film (303) on the cleaned back field region (10) and the non-back field region; After printing a protective paste (401) on the transparent conductive film (303) in the non-back field area, an initial semi-finished product is obtained; After the initial semi-finished product is cleaned and textured, the non-back field area is divided into an isolation area (30) and an emitter area (20), and a textured surface structure (501) is formed on the isolation area and the other side of the N-type single crystal silicon wafer (101) to obtain a semi-finished product; Anti-reflection films (502) are deposited on both sides of the semi-finished product, and metal electrodes (601) are prepared in the emitter region and the back field region to obtain a back-contact solar cell with a double passivation structure.

9. The method according to claim 8, characterized in that The material of the mask layer (203) includes at least one of the following: silicon dioxide, silicon oxynitride, silicon nitride, and the thickness of the mask layer (203) is 30-200 nm.

10. The method according to claim 8, characterized in that The film opening width is 0-1000μm.

Images