TOPCon solar cell with selective passivation contact structure and preparation method thereof

Abstract

The invention discloses a TOPCon solar cell with a selective passivation contact structure and a preparation method of the TOPCon solar cell, and belongs to the technical field of crystalline silicon solar cells. The TOPCon solar cell with the selective passivation contact structure comprises an n-type crystalline silicon substrate, a p + emitter layer, a silicon nitride antireflection layer, a plurality of slots, a plurality of metal electrode structures, a second tunneling oxide layer, an n + polycrystalline silicon layer, a silicon nitride passivation layer and a plurality of Ag electrodes. The low contact resistivity of the metal contact area is ensured, parasitic light absorption loss of the non-metal contact area is avoided, the short-circuit current density and the filling factor of the cell can be improved, the selective passivation contact structure is also arranged on the back surface, the low contact resistivity of the metal contact area can be maintained, and the service life of the cell is prolonged. The parasitic light absorption loss of the non-metal contact area is reduced, the short-circuit current density of the cell can be improved, and the open-circuit voltage of the cell is kept unchanged.

Description

Technical Field

[0001] The invention belongs to the technical field of crystalline silicon solar cells, and in particular relates to a TOPCon solar cell with a selective passivation contact structure and a preparation method thereof. Background Art

[0002] The tunneling oxide passivation contact (TOPCon) structure consists of a tunneling silicon oxide (SiO2) layer and a doped polysilicon (poly-Si) layer, and has the advantages of full-area passivation contact and compatibility with high-temperature production line processes.

[0003] Currently, TOPCon solar cells have achieved a high efficiency of 26.9%. However, the thicker polycrystalline silicon layer in the TOPCon structure is generally formed by high-temperature annealing of amorphous silicon. After annealing, a certain proportion of amorphous silicon is still retained. Amorphous silicon has serious parasitic photon absorption losses, which limits the application scope of the TOPCon structure. Summary of the invention

[0004] In order to solve the problems raised in the above background technology, the present invention provides a TOPCon solar cell with a selective passivation contact structure and a preparation method thereof, so as to solve the problem in the prior art that amorphous silicon in the TOPCon structure has serious parasitic absorption losses of photons, which limits the application scope of the TOPCon structure.

[0005] To achieve the above object, the present invention provides the following technical solutions: TOPCon solar cells with selectively passivated contact structures include: n-type crystalline silicon substrate; p ＋ Emitter layer; p ＋ The emitter layer is arranged on the top surface of the n-type crystalline silicon substrate; Aluminum oxide passivation layer; the aluminum oxide passivation layer is set on p ＋ On the emitter layer; Silicon nitride anti-reflection layer; the silicon nitride anti-reflection layer is arranged on the aluminum oxide passivation layer; At least one groove; the groove is set through the aluminum oxide passivation layer and the silicon nitride anti-reflection layer, and the bottom of the groove is p ＋ a top surface of the emitter layer; At least one metal electrode structure; a metal electrode structure is disposed in a groove, the metal electrode structure comprising a first tunneling oxide layer, a p ＋ Polysilicon layer and Ag / Al electrode, the first tunnel oxide layer is set on p ＋ On the emitter layer, p ＋ The polysilicon layer is disposed on the first tunnel oxide layer, and the Ag / Al electrode is disposed on the p ＋ On the polysilicon layer; A second tunneling oxide layer; the second tunneling oxide layer is arranged on the bottom surface of the n-type crystalline silicon substrate; n ＋ Polysilicon layer; n ＋ The polysilicon layer is disposed on the bottom surface of the second tunnel oxide layer. ＋ The bottom surface of the polysilicon layer is provided with at least one protruding end; Silicon nitride passivation layer; Silicon nitride passivation layer is laid on n ＋ The bottom surface of the polysilicon layer and the silicon nitride passivation layer cover the raised end; At least one Ag electrode; one Ag electrode passes through the silicon nitride passivation layer and is connected to one protruding end.

[0006] Preferably, the thickness of the first tunnel oxide layer and the second tunnel oxide layer are both 1-2 nm.

[0007] Preferably, p ＋ The thickness of the polysilicon layer is 120-200nm, the width is 50-100mm, and the p ＋ The boron doping concentration of the polysilicon layer is 5×10 18 -1×10 20 cm -3 .

[0008] Preferably, n + The width of the polysilicon layer is 60-120 mm, n + The thickness of the polysilicon layer is 10-50nm at its thinnest part and 100-150nm at its thickest part. + The phosphorus doping concentration of the polysilicon layer is 6×10 19 -8×10 20 cm -3 .

[0009] A method for preparing a TOPCon solar cell with a selective passivation contact structure comprises the following steps: S1: pre-treating the n-type crystalline silicon substrate; S2: silicon oxide is deposited on the front and back sides of the pretreated n-type crystalline silicon substrate to form a first tunneling oxide layer and a second tunneling oxide layer, respectively, polysilicon is deposited on the first tunneling oxide layer and the second tunneling oxide layer, and borane is introduced during the deposition of the polysilicon in the first tunneling oxide layer to obtain polysilicon. + The polysilicon layer is deposited by introducing phosphine during the deposition of the second tunnel oxide layer polysilicon to obtain n + Polysilicon layer; S3: performing laser oxidation treatment on the back and front sides of the n-type crystalline silicon substrate after deposition to form a silicon oxide protective layer. The laser oxidation treatment area is the metal contact area of ​​the n-type crystalline silicon substrate where the metal fine grid lines need to be printed; S4: wet-etching the back and front sides of the n-type crystalline silicon substrate after laser oxidation to remove the n + The area without silicon oxide protective layer in the polysilicon layer is etched to a preset thickness. + All regions of the polysilicon layer and the first tunnel oxide layer without the silicon oxide protective layer are etched; S5: removing the silicon oxide protective layer of the n-type crystalline silicon substrate after the wet etching process to obtain a silicon wafer with a selective passivation contact structure; S6: depositing silicon nitride on the back side of the silicon wafer to form a silicon nitride passivation layer, and depositing aluminum oxide and silicon nitride in sequence on the front side of the silicon wafer to form an aluminum oxide passivation layer and a silicon nitride anti-reflection layer; S7: p on silicon wafer + Ag / Al electrodes are printed on the polysilicon layer, and Ag electrodes are printed on the silicon nitride passivation layer of the silicon wafer. The Ag electrodes pass through the silicon nitride passivation layer and the n + The polysilicon layers are connected and co-sintered to obtain a TOPCon solar cell with a selective passivation contact structure.

[0010] Preferably, S1 is specifically: after removing the damaged layer, front surface boron diffusion doping, and back surface polishing of an industrial-grade n-type Cz single crystal silicon wafer with a thickness of 120-150μm, a resistivity of 0.5-2Ω‧cm, and a crystal orientation of (100), an n-type crystalline silicon substrate with an emitter square resistance of 120-140Ω / □ and a junction depth of 0.8-1.2μm is obtained.

[0011] Preferably, in S2, the thicknesses of silicon oxide and polysilicon are 1-2 nm and 100-150 nm respectively, wherein the silicon oxide growth temperature is 590-610°C, and the polysilicon deposition temperature is 600-630°C.

[0012] Preferably, in S4, the wet etching process uses a KOH solution, and the concentration and temperature of the KOH solution are 8-10% and 60-80° C., respectively.

[0013] Preferably, in S5, the silicon oxide protective layer is removed by HF solution.

[0014] Preferably, the thickness of the silicon nitride passivation layer is 90-120 nm, and the thickness of the aluminum oxide passivation layer and the silicon nitride anti-reflection layer are 3-5 nm and 70-80 nm, respectively.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This application uses a method combining laser oxidation and selective etching to achieve different thicknesses of polysilicon in the metal contact area and the non-metal contact area. Compared with the traditional TOPCon solar cell, the selective passivation contact structure of the front side of the TOPCon solar cell of this application not only ensures the low contact resistivity of the metal contact area, but also avoids the parasitic light absorption loss of the non-metal contact area, which can improve the short-circuit current density and fill factor of the battery; 2. Compared with traditional TOPCon solar cells, the selective passivation contact structure on the back of the TOPCon solar cell of the present application also maintains the low contact resistivity of the metal contact area and reduces the parasitic light absorption loss in the non-metal contact area, which can increase the short-circuit current density of the battery, while keeping the open-circuit voltage of the battery unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the specific structure of this application; Figure 2 It is a schematic diagram of the structure of the n-type crystalline silicon substrate after deposition; The accompanying drawings are marked as follows: 1-n-type crystalline silicon substrate, 2-p ＋ Emitter layer, 3-aluminum oxide passivation layer, 4-silicon nitride anti-reflection layer, 5-first tunneling oxide layer; 6-p ＋ Polysilicon layer; 7-Ag / Al electrode; 8-second tunneling oxide layer; 9-n + Polysilicon layer; 10-protruding end; 11-silicon nitride passivation layer; 12-Ag electrode. DETAILED DESCRIPTION

[0017] In order to facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] Embodiment 1: TOPCon solar cells with selectively passivated contact structures include: n-type crystalline silicon substrate 1; p ＋ Emitter layer 2; p ＋ The emitter layer 2 is arranged on the top surface of the n-type crystalline silicon substrate 1; Aluminum oxide passivation layer 3; Aluminum oxide passivation layer 3 is arranged on p ＋ On the emitter layer 2; Silicon nitride anti-reflection layer 4; the silicon nitride anti-reflection layer 4 is arranged on the aluminum oxide passivation layer 3; A plurality of grooves; the grooves are arranged through the aluminum oxide passivation layer 3 and the silicon nitride anti-reflection layer 4, and the bottom of the groove is p ＋a top surface of the emitter layer 2; A plurality of metal electrode structures; a metal electrode structure is arranged in a groove, the metal electrode structure comprises a first tunneling oxide layer 5, p ＋ The polysilicon layer 6 and the Ag / Al electrode 7, the first tunnel oxide layer 5 are arranged on the p ＋ On the emitter layer 2, p ＋ The polysilicon layer 6 is disposed on the first tunnel oxide layer 5, and the Ag / Al electrode 7 is disposed on the p ＋ On the polysilicon layer 6, p ＋ The thickness of the polysilicon layer 6 is 150 nm, the width is 75 mm, and the p ＋ The boron doping concentration of the polysilicon layer 6 is 1×10 19 cm -3 ; A second tunneling oxide layer 8; the second tunneling oxide layer 8 is disposed on the bottom surface of the n-type crystalline silicon substrate 1, and the thickness of the first tunneling oxide layer 5 and the second tunneling oxide layer 8 are both 1.5 nm; n ＋ Polysilicon layer 9; n ＋ The polysilicon layer 9 is disposed on the bottom surface of the second tunnel oxide layer 8. ＋ The bottom surface of the polysilicon layer 9 is provided with a plurality of protrusions 10. The width of the n+ polysilicon layer 9 is 95 mm. The thickness of the n+ polysilicon layer 9 is 20 nm at the thinnest part and 150 nm at the thickest part. The phosphorus doping concentration of the n+ polysilicon layer 9 is 5×10 20 cm -3 ; Silicon nitride passivation layer 11; Silicon nitride passivation layer 11 is laid on n ＋ On the bottom surface of the polysilicon layer 9, a silicon nitride passivation layer 11 covers the protruding end 10; A plurality of Ag electrodes 12 ; one Ag electrode 12 passes through the silicon nitride passivation layer 11 and is connected to one protruding end 10 .

[0019] A method for preparing a TOPCon solar cell with a selective passivation contact structure comprises the following steps: S1: After removing the damaged layer, front surface boron diffusion doping, and back surface polishing of an industrial-grade n-type Cz single-crystalline silicon wafer with a thickness of 120 μm, a resistivity of 0.6 Ω‧cm, and a crystal orientation of (100), an n-type crystalline silicon substrate 1 with an emitter square resistance of 135 Ω / □ and a junction depth of 0.9 μm is obtained; S2: placing the n-type crystalline silicon substrate 1 obtained in S1 in a low pressure chemical vapor deposition LPCVD device, depositing silicon oxide with a thickness of 1000 Å on the front and back sides thereof, respectively forming a first tunneling oxide layer 5 and a second tunneling oxide layer 8, depositing polycrystalline silicon on the first tunneling oxide layer 5 and the second tunneling oxide layer 8, and introducing borane during the deposition of the polycrystalline silicon in the first tunneling oxide layer 5, to obtain p +The polysilicon layer 6 is deposited by introducing phosphine during the deposition of the polysilicon of the second tunnel oxide layer 8 to obtain n + Polysilicon layer 9, silicon oxide and polysilicon thicknesses are 1.5 nm and 150 nm respectively, wherein the silicon oxide growth temperature is 595° C., and the polysilicon deposition temperature is 615° C.; S3: laser oxidation treatment is performed on the back and front sides of the n-type crystalline silicon substrate 1 after deposition to form a silicon oxide protective layer with a thickness of 5 nm. The laser oxidation treatment area is the metal contact area of ​​the n-type crystalline silicon substrate 1 where the metal fine grid lines need to be printed. The laser wavelength is 355 nm, and the spot sizes on the back and front sides are adjusted to 50 and 40 mm respectively. S4: wet-etching the back and front sides of the n-type crystalline silicon substrate 1 after laser oxidation to remove the n + The area without silicon oxide protective layer in the polysilicon layer 9 is etched, n + The thickness of the polysilicon layer 9 is 20 nm at the thinnest part and 95 nm at the thickest part. + The areas without silicon oxide protective layer in the polysilicon layer 6 and the first tunnel oxide layer 5 are all etched, and the width of the unetched area is 75 mm. The wet etching process uses KOH solution, and the concentration and temperature of the KOH solution are 10% and 70° C. respectively; S5: removing the silicon oxide protective layer of the n-type crystalline silicon substrate 1 after the wet etching process by using an HF solution. Since the back side is protected by polysilicon, the tunneling oxide layer on the back side is retained, and the oxide layer on the non-metallic contact area on the front side is removed, thereby obtaining a silicon wafer with a selective passivation contact structure; S6: depositing silicon nitride on the back side of the silicon wafer to form a silicon nitride passivation layer 11, and depositing aluminum oxide and silicon nitride in sequence on the front side of the silicon wafer to form an aluminum oxide passivation layer 3 and a silicon nitride anti-reflection layer 4, wherein the thickness of the silicon nitride passivation layer 11 is 110 nm, and the thicknesses of the aluminum oxide passivation layer 3 and the silicon nitride anti-reflection layer 4 are 4 nm and 80 nm, respectively; S7: p on silicon wafer + The Ag / Al electrode 7 is printed on the polysilicon layer 6, and the Ag electrode 12 is printed on the silicon nitride passivation layer 11 of the silicon wafer. The Ag electrode 12 passes through the silicon nitride passivation layer 11 and the n + The polysilicon layer 9 is connected, wherein the width of the Ag electrode 12 is 45 mm, and the width of the Ag / Al electrode 7 is 35 mm. Finally, after co-sintering in an infrared belt sintering furnace, a TOPCon solar cell with a selective passivation contact structure is obtained.

[0020] In this embodiment, compared with the traditional TOPCon solar cell, the selective passivation contact structure on the front side of the TOPCon solar cell of the present application not only ensures the low contact resistivity of the metal contact area, but also avoids the parasitic light absorption loss in the non-metal contact area, and can improve the short-circuit current density and fill factor of the battery; compared with the traditional TOPCon solar cell, the selective passivation contact structure on the back side of the TOPCon solar cell of the present application also maintains the low contact resistivity of the metal contact area, and reduces the parasitic light absorption loss in the non-metal contact area, and can improve the short-circuit current density of the battery, while the open circuit voltage of the battery remains unchanged; the present application also adopts a laser oxidation method, which has the advantages of high precision, simple process, and short time consumption, and has a high degree of matching with the screen-printed metal grid line, ensuring the smooth preparation of high-efficiency TOPCon solar cells.

[0021] While the experiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made thereto without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A TOPCon solar cell with a selectively passivated contact structure, characterized in that: include: n-type crystalline silicon substrate (1); p ＋ Emitter layer (2); p ＋ The emitter layer (2) is arranged on the top surface of the n-type crystalline silicon substrate (1); Aluminum oxide passivation layer (3); the aluminum oxide passivation layer (3) is arranged on p ＋ On the emitter layer (2); A silicon nitride anti-reflection layer (4); the silicon nitride anti-reflection layer (4) is arranged on the aluminum oxide passivation layer (3); At least one groove; the groove is arranged to penetrate the aluminum oxide passivation layer (3) and the silicon nitride anti-reflection layer (4), and the bottom of the groove is p ＋ a top surface of the emitter layer (2); At least one metal electrode structure; a metal electrode structure is arranged in a groove, and the metal electrode structure includes a first tunneling oxide layer (5), a p ＋ The polysilicon layer (6) and the Ag / Al electrode (7), the first tunnel oxide layer (5) are arranged on the p ＋ On the emitter layer (2), p ＋ The polysilicon layer (6) is arranged on the first tunneling oxide layer (5), and the Ag / Al electrode (7) is arranged on the p ＋ On the polysilicon layer (6); A second tunneling oxide layer (8); the second tunneling oxide layer (8) is arranged on the bottom surface of the n-type crystalline silicon substrate (1); n ＋ Polysilicon layer (9); n ＋ The polysilicon layer (9) is arranged on the bottom surface of the second tunnel oxide layer (8), n ＋ The bottom surface of the polysilicon layer (9) is provided with at least one protruding end (10); Silicon nitride passivation layer (11); the silicon nitride passivation layer (11) is laid on n ＋ The bottom surface of the polysilicon layer (9) and the silicon nitride passivation layer (11) cover the protruding end (10); At least one Ag electrode (12); an Ag electrode (12) passes through the silicon nitride passivation layer (11) and is connected to a protruding end (10).

2. The TOPCon solar cell with a selective passivation contact structure according to claim 1, characterized in that: The thickness of the first tunneling oxide layer (5) and the second tunneling oxide layer (8) are both 1-2 nm.

3. The TOPCon solar cell with a selective passivation contact structure according to claim 1, characterized in that: p ＋ The thickness of the polysilicon layer (6) is 120-200 nm, the width is 50-100 mm, and the p ＋ The boron doping concentration of the polysilicon layer (6) is 5×10 18 -1×10 20 cm -3 .

4. The TOPCon solar cell with a selective passivation contact structure according to claim 1, characterized in that: The width of the n+ polysilicon layer (9) is 60-120 mm, the thickness of the n+ polysilicon layer (9) at its thinnest point is 10-50 nm, and the thickness of the n+ polysilicon layer (9) at its thickest point is 100-150 nm. The phosphorus doping concentration of the n+ polysilicon layer (9) is 6×10 19 -8×10 20 cm -3 .

5. The method for preparing a TOPCon solar cell with a selective passivation contact structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: pre-treating an n-type crystalline silicon substrate (1); S2: depositing silicon oxide on the front and back sides of the pre-treated n-type crystalline silicon substrate (1) to form a first tunneling oxide layer (5) and a second tunneling oxide layer (8), respectively; depositing polysilicon on the first tunneling oxide layer (5) and the second tunneling oxide layer (8); and introducing borane during the deposition of the polysilicon on the first tunneling oxide layer (5) to obtain polysilicon. + A polysilicon layer (6), during the deposition process of the polysilicon of the second tunnel oxide layer (8), phosphine is introduced to obtain an n+ polysilicon layer (9); S3: performing laser oxidation treatment on the back and front sides of the n-type crystalline silicon substrate (1) after deposition to form a silicon oxide protective layer, wherein the laser oxidation treatment area is a metal contact area of ​​the n-type crystalline silicon substrate (1) where metal fine grid lines are to be printed; S4: wet-etching the back and front sides of the laser-oxidized n-type crystalline silicon substrate (1) to remove the n + The area without silicon oxide protective layer in the polysilicon layer (9) is etched to a preset thickness, + All areas of the polysilicon layer (6) and the first tunneling oxide layer (5) that are free of the silicon oxide protective layer are etched; S5: removing the silicon oxide protective layer of the n-type crystalline silicon substrate (1) after the wet etching process, to obtain a silicon wafer having a selective passivation contact structure; S6: depositing silicon nitride on the back side of the silicon wafer to form a silicon nitride passivation layer (11), and depositing aluminum oxide and silicon nitride in sequence on the front side of the silicon wafer to form an aluminum oxide passivation layer (3) and a silicon nitride anti-reflection layer (4); S7: p on silicon wafer + An Ag / Al electrode (7) is printed on the polysilicon layer (6), and an Ag electrode (12) is printed on the silicon nitride passivation layer (11) of the silicon wafer. The Ag electrode (12) passes through the silicon nitride passivation layer (11) and the n + The polysilicon layers (9) are connected and co-sintered to obtain a TOPCon solar cell with a selective passivation contact structure.

6. The method for preparing a TOPCon solar cell according to claim 5, characterized in that: S1 is specifically as follows: after removing the damaged layer, performing front surface boron diffusion doping, and back surface polishing on an industrial-grade n-type Cz single crystal silicon wafer with a thickness of 120-150 μm, a resistivity of 0.5-2 Ω‧cm, and a crystal orientation of (100), an n-type crystalline silicon substrate (1) with an emitter square resistance of 120-140 Ω / □ and a junction depth of 0.8-1.2 μm is obtained.

7. The method for preparing a TOPCon solar cell according to claim 5, characterized in that: In S2, the thicknesses of silicon oxide and polysilicon are 1-2 nm and 100-150 nm respectively, wherein the silicon oxide growth temperature is 590-610°C, and the polysilicon deposition temperature is 600-630°C.

8. The method for preparing a TOPCon solar cell according to claim 5, characterized in that: In S4, the wet etching process uses a KOH solution, and the concentration and temperature of the KOH solution are 8-10% and 60-80° C., respectively.

9. The method for preparing a TOPCon solar cell according to claim 5, characterized in that: In S5, the silicon oxide protective layer is removed by HF solution.

10. The method for preparing a TOPCon solar cell according to claim 5, characterized in that: The thickness of the silicon nitride passivation layer (11) is 90-120 nm, and the thickness of the aluminum oxide passivation layer (3) and the silicon nitride anti-reflection layer (4) are 3-5 nm and 70-80 nm respectively.

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