TBC solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, in particular to a TBC solar cell and a preparation method thereof.The front face of the TBC solar cell is sequentially provided with an aluminum oxide and silicon nitride antireflection film, a suede structure and an N-type monocrystalline silicon wafer from outside to inside; the back surface field region comprises a metal electrode, an aluminum oxide and silicon nitride antireflection film, a phosphorus-doped polycrystalline silicon layer, a first tunneling oxide layer and an N-type monocrystalline silicon wafer from outside to inside in sequence; the emitter region comprises a metal electrode, an aluminum oxide + silicon nitride antireflection film, a second boron-doped polycrystalline silicon layer, a third tunneling oxide layer, a first boron-doped polycrystalline silicon layer, a second tunneling oxide layer and an N-type monocrystalline silicon wafer from outside to inside in sequence; and the isolation area comprises an aluminum oxide and silicon nitride antireflection film, a suede structure and an N-type monocrystalline silicon wafer from outside to inside in sequence. And the phosphorus-doped polycrystalline silicon and the boron-doped polycrystalline silicon are simultaneously subjected to high-temperature retreatment through a one-step annealing process, so that the process steps of the TBC battery are further shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a TBC solar cell and a preparation method thereof. Background Art

[0002] TBC cells (Tunneling Oxide Passivated Contact Back Contact) are widely used due to their good surface passivation effect and metal contact performance. However, the current preparation process of TBC cells involves complex processes and numerous steps. Summary of the Invention

[0003] The purpose of the present invention is to provide a TBC solar cell and a preparation method thereof to solve the above technical problems.

[0004] To achieve the above purpose, the present invention provides a TBC solar cell. The front side of the TBC solar cell from outside to inside is successively: an alumina + silicon nitride antireflection film, a textured structure, an N-type monocrystalline silicon wafer; the back side of the TBC solar cell is divided into a back field region, an emitter region, an isolation region between the back field region and the emitter region; the back field region from outside to inside is successively: a metal electrode, an alumina + silicon nitride antireflection film, a phosphorus-doped polysilicon layer, a first tunneling oxide layer, an N-type monocrystalline silicon wafer; the emitter region from outside to inside is successively: a metal electrode, an alumina + silicon nitride antireflection film, a second boron-doped polysilicon layer, a third tunneling oxide layer, a first boron-doped polysilicon layer, a second tunneling oxide layer, an N-type monocrystalline silicon wafer; the isolation region from outside to inside is successively: an alumina + silicon nitride antireflection film, a textured structure, an N-type monocrystalline silicon wafer.

[0005] The present invention also provides a preparation method of a TBC solar cell, and the method includes:

[0006] Depositing a first tunneling oxide layer, a phosphorus-doped polysilicon layer and a mask layer successively on one side of an N-type monocrystalline silicon wafer;

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

[0008] Depositing a second tunneling oxide layer, a first intrinsic polysilicon layer, a third tunneling oxide layer, a second intrinsic polysilicon layer and a borosilicate glass layer successively on the cleaned back field region and non-back field region;

[0009] After selectively laser doping the borosilicate glass layer in the non-back field region, dividing the non-back field region into an isolation region and an emitter region by cleaning and texturing, and forming a textured structure on the other side of the isolation region and the N-type monocrystalline silicon wafer to obtain an initial semi-finished product;

[0010] After annealing the initial semi-finished product, a semi-finished product is obtained. An anti-reflection film of aluminum oxide + silicon nitride is deposited on both sides of the semi-finished product, and metal electrodes are prepared in the emitter region and the back field region to obtain a TBC solar cell.

[0011] Technical effects and advantages of the present invention:

[0012] 1. Deposit the first tunneling oxide layer, phosphorus-doped polysilicon layer, and mask layer in one step by a single device. Then, the emitter region is reserved by patterning (by using methods such as laser opening, printing etching paste for opening, or printing protective paste in regions with opposite polarities, but not limited to these several methods). This method can fabricate a patterned N-type polysilicon region with the shortest process steps.

[0013] 2. Deposit the second tunneling oxide layer, the first intrinsic polysilicon layer, the third tunneling oxide layer, the second intrinsic polysilicon layer, and the borosilicate glass layer in one go above the opened film region. Use a laser device to laser-heat the region of the borosilicate glass layer to be processed, so that the second intrinsic polysilicon layer is transformed into a P-type polysilicon region with a high doping concentration (i.e., the second boron-doped polysilicon layer). After annealing, the third tunneling oxide layer blocks some boron atoms from entering the first intrinsic polysilicon layer, causing the first intrinsic polysilicon layer to be transformed into a P-type polysilicon with a low doping concentration (i.e., the first boron-doped polysilicon layer), and the second tunneling oxide layer blocks some boron atoms from entering the silicon substrate again. In this way of double-layer tunneling oxide + double-layer polysilicon, boron atoms are blocked from entering the silicon substrate, and more boron atoms are retained in the P-type polysilicon layer, increasing the boron doping concentration of the P-type polysilicon and reducing the boron atom doping concentration on the surface of the silicon substrate, thereby improving the surface passivation performance and metal contact performance of the emitter region. Of course, it is not limited to using the double-layer tunneling oxide + double-layer polysilicon method to improve the surface passivation performance of P-type polysilicon, and more than two layers of tunneling oxide + polysilicon can also be used to achieve it.

[0014] 3. Simultaneously perform high-temperature reprocessing on phosphorus-doped polysilicon and boron-doped polysilicon through a one-step annealing process, further shortening the process steps of the TBC cell and solving the problem of excessive leakage current in the TBC cell.

[0015] Other features and advantages of the present invention will be described in the subsequent specification, and some of them will be obvious from the specification or understood by implementing the present invention. Description of the Drawings

[0016] 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 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.

[0017] Figure 1 is the structural diagram of the TBC solar cell;

[0018] Figure 2 is the structural diagram after depositing the first tunneling oxide layer, phosphorus-doped polysilicon layer, and mask layer;

[0019] Figure 3 is the structural diagram after laser opening the film;

[0020] Figure 4 is the structural diagram after depositing the second tunneling oxide layer, first intrinsic polysilicon layer, third tunneling oxide layer, and second intrinsic polysilicon layer;

[0021] Figure 5 is the structural diagram after depositing the borosilicate glass layer;

[0022] Figure 6 is the structural diagram after selective laser doping;

[0023] Figure 7 is the structural diagram after cleaning, texturing, and annealing;

[0024] Figure 8 is the structural diagram after depositing the aluminum oxide and silicon nitride antireflection films;

[0025] Reference numerals: 101, N-type monocrystalline silicon wafer; 201, first tunneling oxide layer; 202, phosphorus-doped polysilicon layer; 203, mask layer; 201', second tunneling oxide layer; 301, first intrinsic polysilicon layer; 201'', third tunneling oxide layer; 301', second intrinsic polysilicon layer; 401, borosilicate glass layer; 501, textured structure; 502, aluminum oxide + silicon nitride antireflection film; 601, metal electrode; 301''', first boron-doped polysilicon layer; 301'', second boron-doped polysilicon layer; 10, back field region; 20, emitter region; 30, isolation region. Detailed implementation manners

[0026] 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.

[0027] It should be noted that the structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they do not have substantial technical significance. Any modification of the structure, change in 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 of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope within which the present invention can be implemented.

[0028] To solve the deficiencies of the prior art, the present invention discloses a TBC solar cell, as Figure 1 shown. The front side of the TBC solar cell from outside to inside is: aluminum oxide + silicon nitride antireflection film 502, textured structure 501, N-type monocrystalline silicon wafer 101; the back side of the TBC 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 from outside to inside is: metal electrode 601, aluminum oxide + silicon nitride antireflection film 502, phosphorus-doped polysilicon layer 202, first tunneling oxide layer 201, N-type monocrystalline silicon wafer 101; the emitter region from outside to inside is: metal electrode 601, aluminum oxide + silicon nitride antireflection film 502, second boron-doped polysilicon layer 301, third tunneling oxide layer 201", first boron-doped polysilicon layer 301"', second tunneling oxide layer 201', N-type monocrystalline silicon wafer 101; the isolation region from outside to inside is: aluminum oxide + silicon nitride antireflection film 502, textured structure 501, N-type monocrystalline silicon wafer 101.

[0029] The present invention also provides a preparation method for the TBC solar cell, and the specific steps are as follows:

[0030] S1. Select the N-type monocrystalline silicon wafer 101 as the substrate and perform surface damage removal treatment.

[0031] Among them, the thickness of the N-type silicon wafer is 50 - 300 μm, preferably 82 - 210 μm, more preferably 128 - 188 μm, and the resistivity is 0.1 - 50 Ω·cm, preferably 16 - 41 Ω·cm, 24 - 35 Ω·cm.

[0032] S2. Deposit the first tunneling oxide layer 201, phosphorus-doped polysilicon layer 202, and mask layer 203 on the N-type monocrystalline silicon wafer 101 in one step, as Figure 2 shown.

[0033] Among them, the thickness of the first tunneling oxide layer is 0.1 - 5 nm, preferably 0.6 - 4.1 nm, and more preferably 1.6 - 2.9 nm.

[0034] Among them, the thickness of the phosphorus-doped polysilicon layer is 10 - 300 nm, preferably 61 - 235 nm, and more preferably 92 - 168 nm. The surface doping concentration is 1×10 20 cm -3 -1×10 21 cm -3 , preferably

[0035] 1.2×10 20 cm -3 -0.8×10 21 cm -3 , more preferably 1.6×10 20 cm -3 -0.4×10 21 cm -3 .

[0036] 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. The thickness of the mask layer is 30 - 200 nm, preferably 62 - 156 nm, and more preferably 94 - 135 nm.

[0037] S3. Open a film on the mask layer (using methods such as laser film opening or printing and etching slurry for film opening or printing protective slurry in regions with opposite polarities, but not limited to these several methods) to reserve a non-back field region, and then polish and clean, as Figure 3 shown.

[0038] Among them, the film opening width is 0 - 1000 μm, preferably 210 - 860 μm, and more preferably 430 - 610 μm.

[0039] S4. Deposit a second tunneling oxide layer 201', a first intrinsic polysilicon layer 301, a third tunneling oxide layer 201'', and a second intrinsic polysilicon layer 301' in the non-back field region on the back of the battery, as Figure 4 shown.

[0040] Among them, the thickness of the second tunneling oxide layer is 0.1 - 5 nm, preferably 1.1 - 3.9 nm, and more preferably 1.8 - 2.3 nm.

[0041] Among them, the thickness of the first intrinsic polysilicon layer is 10 - 200 nm, preferably 55 - 161 nm, and more preferably 98 - 135 nm.

[0042] Among them, the thickness of the third tunneling oxide layer is 0.1 - 5 nm, preferably 1.1 - 4.1 nm, and more preferably 2.3 - 3.4 nm.

[0043] Among them, the thickness of the second intrinsic polysilicon layer is 50 - 300 nm, preferably 98 - 223 nm, and more preferably 140 - 190 nm.

[0044] S5. Deposit a borosilicate glass layer 401 on the second intrinsic polysilicon layer 301', as Figure 5 shown.

[0045] Among them, the thickness of the borosilicate glass layer is 10 - 100 nm, preferably 35 - 84 nm, and more preferably 45 - 65 nm.

[0046] S6. Perform selective laser doping or laser heating on the borosilicate glass layer 401, as Figure 6 shown.

[0047] S7. Clean and texture the semi-finished product prepared in S6 to form a textured surface structure 501 (such as a pyramid or an inverted pyramid) in the isolation areas on the front and back of the battery, and perform annealing treatment on both P-type polysilicon and N-type polysilicon simultaneously. After annealing, the surface doping concentration of the first boron-doped polysilicon layer 301''' corresponding to the first intrinsic polysilicon layer 301 is 5×10 18 cm -3 -5×10 19 cm -3 Preferably, it is 6.4×10 18 cm -3 -3.1×10 19 cm -3 More preferably, it is 8.1×10 18 cm -3 -1.2×10 19 cm -3 The surface doping concentration of the second boron-doped polysilicon layer 301'' corresponding to the second intrinsic polysilicon layer 301' is

[0048] 5×10 19 cm -3 -1×10 20 cm -3 Preferably, it is 7.2×10 19 cm -3 -0.6×10 20 cm -3 More preferably, it is 9.1×10 19 cm -3 -0.3×10 20 cm -3 The annealing temperature is 500 - 1000 °C, and the annealing time is 10 - 120 min, as Figure 7 shown.

[0049] S8. Deposit an anti-reflection film 502 of aluminum oxide + silicon nitride on both sides of the semi-finished product prepared in S7, as Figure 8 shown.

[0050] S9. Print metal electrodes 601 in the emitter region and the back surface field region, and then fabricate a TBC cell, as Figure 1 shown.

[0051] The present invention prepares the first tunneling oxide layer, the phosphorus-doped polysilicon layer and the mask layer through a one-step process, prepares the boron-doped polysilicon region by selective laser doping + cleaning, and finally performs a high-temperature re-treatment on the phosphorus-doped polysilicon layer and the boron-doped polysilicon region simultaneously by a one-step annealing process, greatly reducing the manufacturing process flow of the TBC cell. An isolation area is left between the emitter and the back surface field, solving the problem of leakage of the TBC cell. All the technical solutions of the whole set use conventional domestic equipment, the process flow is simple, and the manufacturing cost is low, which is especially suitable for industrial manufacturing.

[0052] 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, for those skilled in the art, they 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 in the protection scope of the present invention.

Claims

1. A TBC solar cell, characterized in that: The front side of the TBC solar cell is composed of, from outside to inside: an aluminum oxide + silicon nitride anti-reflection film (502), a velvet structure (501), and an N-type single crystal silicon wafer (101); the back side of the TBC 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) is composed of, from outside to inside: a metal electrode (601), an aluminum oxide + silicon nitride anti-reflection film (502), a phosphorus-doped polysilicon layer (202), a first tunneling oxide layer (201), an N-type A single crystal silicon wafer (101); the emitter region (20) comprises, from outside to inside: a metal electrode (601), an aluminum oxide + silicon nitride anti-reflection film (502), a second boron-doped polysilicon layer (301"), a third tunneling oxide layer (201"), a first boron-doped polysilicon layer (301")'), a second tunneling oxide layer (201"), and an N-type single crystal silicon wafer (101); the isolation region (30) comprises, from outside to inside: an aluminum oxide + silicon nitride anti-reflection film (502), a velvet structure (501), and an N-type single crystal silicon wafer (101).

2. The TBC 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 TBC 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 TBC solar cell according to claim 1, characterized in that: The thickness of the phosphorus-doped polysilicon layer (202) is 10-300 nm, and the surface doping concentration is 1×10 20 cm -3 -1×10 21 cm -3 .

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

6. The TBC solar cell according to claim 1, characterized in that: The first boron-doped polysilicon layer (301') has a thickness of 10-200 nm and a surface doping concentration of 5 x 10 18 cm -3 -5×10 19 cm -3 .

7. The TBC solar cell according to claim 1, characterized in that: The thickness of the third tunnel oxide layer (201") is 0.1-5 nm.

8. The TBC solar cell according to claim 1, characterized in that: The second boron-doped polysilicon layer (301") has a thickness of 50-300 nm and a surface doping concentration of 5×10 19 cm -3 -1×10 20 cm -3 .

9. A method for preparing a TBC solar cell according to any one of claims 1 to 8, characterized in that: The method comprises: A first tunneling oxide layer (201), a 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; Depositing a second tunneling oxide layer (201'), a first intrinsic polysilicon layer (301), a third tunneling oxide layer (201"), a second intrinsic polysilicon layer (301') and a borosilicate glass layer (401) in sequence on the cleaned back field region and the non-back field region; After selectively laser doping the borosilicate glass layer (401) in the non-back field region, the non-back field region is divided into an isolation region (30) and an emitter region (20) by cleaning and texturing, and a textured surface structure (501) is formed in the isolation region and the other side of the N-type single crystal silicon wafer (101) to obtain an initial semi-finished product; The initial semi-finished product is annealed to obtain a semi-finished product, and an aluminum oxide + silicon nitride anti-reflection film (502) is deposited on both sides of the semi-finished product. A TBC solar cell is obtained after metal electrodes (601) are prepared in the emitter region and the back field region.

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

11. The method according to claim 9, characterized in that The film opening width is 0-1000μm.

12. The method according to claim 9, characterized in that The thickness of the borosilicate glass layer (401) is 10-100 nm.

13. The method according to claim 9, characterized in that The annealing temperature is 500-1000°C and the annealing time is 10-120min.

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