TOPCon solar cell with selective passivation contact structure

Abstract

The utility model discloses a TOPCon solar cell with a selective passivation contact structure, which belongs to the technical field of crystalline silicon solar cells and 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 selective passivation contact structure is arranged on the front face of the TOPCon solar cell, low contact resistivity of a metal contact area is guaranteed, parasitic light absorption loss of a non-metal contact area is avoided, the short-circuit current density and filling factors of the cell can be improved, the selective passivation contact structure is also arranged on the back face of the TOPCon solar cell, and the service life of the TOPCon solar cell is prolonged. The low contact resistivity of the metal contact area can be maintained, the parasitic light absorption loss of the non-metal contact area is reduced, the short-circuit current density of the battery can be improved, and the open-circuit voltage of the battery is kept unchanged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of crystalline silicon solar cells, and particularly relates to a TOPCon solar cell with a selective passivation contact structure. BACKGROUND

[0002] The tunneling oxide passivation contact (TOPCon) structure is composed of a tunneling oxide silicon (SiO2) layer and a doped poly-silicon (poly-Si) layer, and has the advantages of full-area passivation contact and compatible production line high-temperature process.

[0003] At present, the TOPCon solar cell has achieved a high efficiency of 26.9%, but the relatively thick poly-silicon layer in the TOPCon structure is generally formed by high-temperature annealing of amorphous silicon, and a certain proportion of amorphous silicon is still retained after annealing, and the amorphous silicon has serious photon parasitic absorption loss, which limits the application range of the TOPCon structure. SUMMARY

[0004] To solve the problems in the background art, the application provides a TOPCon solar cell with a selective passivation contact structure to solve the problem in the prior art that the amorphous silicon in the TOPCon structure has serious photon parasitic absorption loss, which limits the application range of the TOPCon structure.

[0005] To achieve the above-mentioned purposes, the application provides the following technical solutions.

[0006] The TOPCon solar cell with a selective passivation contact structure comprises:

[0007] An n-type crystalline silicon substrate;

[0008] A p ＋ emitter layer; ＋ The emitter layer is arranged on the top surface of the n-type crystalline silicon substrate;

[0009] An aluminum oxide passivation layer; the aluminum oxide passivation layer is arranged on the p ＋ emitter layer;

[0010] A silicon nitride anti-reflection layer; the silicon nitride anti-reflection layer is arranged on the aluminum oxide passivation layer;

[0011] At least one slot; the slot is arranged through the aluminum oxide passivation layer and the silicon nitride anti-reflection layer, and the bottom of the slot is the top surface of the p ＋ emitter layer;

[0012] At least one metal electrode structure; one metal electrode structure is arranged in one slot, and the metal electrode structure comprises a first tunneling oxide layer, a p ＋ poly-silicon layer and an Ag / Al electrode; the first tunneling oxide layer is arranged on the p ＋ emitter layer, and the p＋ A polysilicon layer is disposed on the first tunneling oxide layer, and an Ag / Al electrode is disposed on the p ＋ polysilicon layer;

[0013] a second tunneling oxide layer; the second tunneling oxide layer is disposed on the bottom surface of the n-type crystalline silicon substrate;

[0014] n ＋ a polysilicon layer; the n ＋ polysilicon layer is disposed on the bottom surface of the second tunneling oxide layer, and the n ＋ The bottom surface of the polysilicon layer is provided with at least one protruding end;

[0015] a silicon nitride passivation layer; the silicon nitride passivation layer is disposed on the bottom surface of the n ＋ polysilicon layer, and the silicon nitride passivation layer covers the protruding end;

[0016] at least one Ag electrode; one Ag electrode is connected to one protruding end through the silicon nitride passivation layer.

[0017] Preferably, the n-type crystalline silicon substrate is an n-type Cz monocrystalline silicon wafer with an emitter sheet resistance of 120-140 Ω / □, a junction depth of 0.8-1.2 μm, a thickness of 120-150 μm, a resistivity of 0.5-2 Ω·cm, and a crystal orientation of (100).

[0018] Preferably, the thickness of the aluminum oxide passivation layer and the thickness of the silicon nitride anti-reflection layer are 3-5 nm and 70-80 nm, respectively.

[0019] Preferably, the thickness of the first tunneling oxide layer and the thickness of the second tunneling oxide layer are both 1-2 nm, and the first tunneling oxide layer and the second tunneling oxide layer are both formed by depositing silicon oxide.

[0020] Preferably, the p ＋ polysilicon layer has a thickness of 120-200 nm and a width of 50-100 mm, and the p ＋ polysilicon layer has a boron doping concentration of 5×10 18 -1×10 20 cm -3 , and the p + polysilicon layer is formed by introducing borane during deposition of the polysilicon.

[0021] Preferably, the n+ polysilicon layer has a width of 60-120 mm, a thickness of 10-50 nm at the thinnest part and a thickness of 100-150 nm at the thickest part, and a phosphorus doping concentration of 6×10 19 -8×10 20 cm -3 , and the n+ polysilicon layer is formed by introducing phosphine during deposition of the polysilicon.

[0022] Preferably, the thickness of the silicon nitride passivation layer is 90-120 nm.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1. The application sets different thicknesses of polysilicon in the electrode contact area and the non-electrode contact area, compared with the conventional TOPCon solar cell, the front selective passivation contact structure of the TOPCon solar cell of the application can ensure low contact resistivity of the electrode contact area and avoid parasitic light absorption loss in the non-electrode contact area, thereby improving the short-circuit current density and the fill factor of the cell.

[0025] 2. Compared with the conventional TOPCon solar cell, the back selective passivation contact structure of the TOPCon solar cell of the application can also maintain low contact resistivity of the electrode contact area and reduce parasitic light absorption loss in the non-electrode contact area, thereby improving the short-circuit current density of the cell, and the open-circuit voltage of the cell remains unchanged. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a specific structural schematic diagram of the application;

[0027] Figure 2 is a structural schematic diagram of the n-type crystalline silicon substrate after deposition is completed;

[0028] The reference signs are as follows:

[0029] 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

[0030] In order to facilitate those skilled in the art to understand the technical content of the application, the application will be further described in detail below in combination with the drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the application and do not limit the application.

[0031] Example 1:

[0032] The TOPCon solar cell with a selective passivation contact structure comprises:

[0033] n-type crystalline silicon substrate 1; the n-type crystalline silicon substrate 1 is an n-type Cz monocrystalline silicon wafer with an emitter sheet resistance of 120-140 Ω / □, a junction depth of 0.8-1.2 μm, a thickness of 120-150 μm, a resistivity of 0.5-2 Ω·cm, and a crystal orientation of (100);

[0034] p ＋ emitter layer 2; the emitter layer 2 is p ＋ emitter layer 2 is disposed on the top surface of the n-type crystalline silicon substrate 1;

[0035] alumina passivation layer 3; the alumina passivation layer 3 is disposed on the p ＋ emitter layer 2;

[0036] silicon nitride anti-reflection layer 4; the silicon nitride anti-reflection layer 4 is disposed on the alumina passivation layer 3;

[0037] a plurality of grooves; the grooves are disposed through the alumina passivation layer 3 and the silicon nitride anti-reflection layer 4, and the groove bottoms are p ＋ emitter layer 2;

[0038] a plurality of metal electrode structures; one metal electrode structure is disposed in one groove, and the metal electrode structure comprises a first tunneling oxide layer 5, a p ＋ polysilicon layer 6, and an Ag / Al electrode 7, the first tunneling oxide layer 5 is disposed on the p ＋ emitter layer 2, the p ＋ polysilicon layer 6 is disposed on the first tunneling oxide layer 5, and the Ag / Al electrode 7 is disposed on the p ＋ polysilicon layer 6, and the p ＋ polysilicon layer 6 has a thickness of 150 nm and a width of 75 mm, and the p ＋ boron doping concentration of the polysilicon layer 6 is 1×10 19 cm -3 ;

[0039] 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 thicknesses of the first tunneling oxide layer 5 and the second tunneling oxide layer 8 are both 1.5 nm;

[0040] n ＋ polysilicon layer 9; the n ＋ polysilicon layer 9 is disposed on the bottom surface of the second tunneling oxide layer 8, and the n ＋ the bottom surface of the n+ polysilicon layer 9 is provided with a plurality of raised ends 10, the width of the n+ polysilicon layer 9 is 95 mm, the thickness of the thinnest part of the n+ polysilicon layer 9 is 20 nm, the thickness of the thickest part of the n+ polysilicon layer 9 is 150 nm, and the phosphorus doping concentration of the n+ polysilicon layer 9 is 5×10 20 cm -3 ;

[0041] Silicon nitride passivation layer 11; silicon nitride passivation layer 11 is laid on n ＋ Polysilicon layer 9 bottom surface, silicon nitride passivation layer 11 covers the protruding end 10;

[0042] Multiple Ag electrodes 12; one Ag electrode 12 is connected with one protruding end 10 through silicon nitride passivation layer 11.

[0043] The preparation method of the TOPCon solar cell with selectively passivated contact structure comprises the following steps:

[0044] S1: After the damage layer, the front surface boron diffusion doping, and the back surface polishing treatment of the n-type Cz single crystal silicon wafer with an industrial thickness of 120 μm, a resistivity of 0.6 Ω·cm, and a crystal direction of 100, an n-type crystalline silicon substrate 1 with an emitter sheet resistance of 135 Ω / □ and a junction depth of 0.9 μm is obtained.

[0045] S2: The n-type crystalline silicon substrate 1 obtained in S1 is placed in a low-pressure chemical vapor deposition (LPCVD) device, and a thickness of silicon oxide is deposited on the front and back surfaces to form a first tunneling oxide layer 5 and a second tunneling oxide layer 8, respectively. Polysilicon is deposited on the first tunneling oxide layer 5 and the second tunneling oxide layer 8. Phosphine is introduced during the deposition of the polysilicon on the first tunneling oxide layer 5 to obtain a p + Polysilicon layer 6, borane is introduced during the deposition of the polysilicon on the second tunneling oxide layer 8 to obtain an n + Polysilicon layer 9, the thicknesses of the silicon oxide and the polysilicon are 1.5 nm and 150 nm, respectively, wherein the silicon oxide growth temperature is 595 ℃, and the polysilicon deposition temperature is 615 ℃;

[0046] S3: Laser oxidation treatment is performed on the back surface and the front surface of the n-type crystalline silicon substrate 1 after the deposition is completed to form a silicon oxide protective layer with a thickness of 5 nm. The laser oxidation treatment area is the electrode contact area of the n-type crystalline silicon substrate 1 where the metal fine grid lines are to be printed. The laser wavelength is 355 nm, and the spot sizes of the back surface and the front surface are adjusted to 50 mm and 40 mm, respectively.

[0047] S4: Wet etching treatment is performed on the back surface and the front surface of the n-type crystalline silicon substrate 1 after the laser oxidation treatment to etch the n + The region without the silicon oxide protective layer in the polysilicon layer 9 is etched, and the n + The thickness of the thin part of the polysilicon layer 9 is 20 nm, and the width of the thick part is 95 mm. The p + The regions without the silicon oxide protective layer in the polysilicon layer 6 and the first tunneling oxide layer 5 are etched, and the width of the unetched region is 75 mm. The wet etching treatment uses KOH solution, and the concentration and temperature of the KOH solution are 10% and 70 ℃, respectively.

[0048] S5: The silicon oxide protective layer of the n-type crystalline silicon substrate 1 after the wet etching treatment is removed by HF solution. Since the back surface is protected by polysilicon, the tunneling oxide layer on the back surface is retained, and the oxide layer on the front surface non-electrode contact area is removed, obtaining a silicon wafer with a selective passivation contact structure;

[0049] S6: Silicon nitride is deposited on the back surface of the silicon wafer to form a silicon nitride passivation layer 11, and aluminum oxide and silicon nitride are sequentially deposited on the front surface of the silicon wafer to form an aluminum oxide passivation layer 3 and a silicon nitride anti-reflection layer 4. The thickness of the silicon nitride passivation layer 11 is 110 nm, and the thickness of the aluminum oxide passivation layer 3 and the silicon nitride anti-reflection layer 4 is 4 nm and 80 nm, respectively.

[0050] S7: The p-type doped emitter layer 5 of the silicon wafer is printed with a polysilicon layer 6, and the n-type doped emitter layer 2 of the silicon wafer is printed with an Ag / Al electrode 7. + The polysilicon layer 6 is printed with an Ag / Al electrode 7, and the silicon nitride passivation layer 11 of the silicon wafer is printed with an Ag electrode 12. The Ag electrode 12 penetrates through the silicon nitride passivation layer 11 and is connected with the n-type doped emitter layer 2. + 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 a co-sintering operation is performed by an infrared belt sintering furnace, a TOPCon solar cell with a selective passivation contact structure is obtained.

[0051] In this embodiment, compared with the conventional TOPCon solar cell, the selective passivation contact structure on the front surface of the TOPCon solar cell of the present application not only ensures the low contact resistivity of the electrode contact area, but also avoids the parasitic light absorption loss of the non-electrode contact area, which can improve the short-circuit current density and the fill factor of the cell. Compared with the conventional TOPCon solar cell, the selective passivation contact structure on the back surface of the TOPCon solar cell of the present application also maintains the low contact resistivity of the electrode contact area and reduces the parasitic light absorption loss of the non-electrode contact area, which can improve the short-circuit current density of the cell, and the open-circuit voltage of the cell remains unchanged. The present application also uses a laser oxidation method, which has the advantages of high precision, simple process, short time-consuming, etc., and has high matching degree with screen-printed metal grid lines, which ensures the smooth preparation of high-efficiency TOPCon solar cells.

[0052] Although the experiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to the experiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A TOPCon solar cell with a selectively passivated contact structure, characterized in that The application relates to a solar cell, which comprises the following parts: 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). An aluminum oxide passivation layer (3) is provided on the p ＋ emitter layer (2). aluminum oxide passivation layer (3); At least one slot; the slot is arranged through the aluminum oxide passivation layer (3) and the silicon nitride anti-reflection layer (4), the bottom of the slot is p ＋ Top surface of the emitter layer (2); at least one metal electrode structure; one metal electrode structure is arranged in one slot, the metal electrode structure comprises a first tunneling oxide layer (5), a p ＋ polysilicon layer (6) and Ag / Al electrode (7), the first tunneling oxide layer (5) is arranged on the p ＋ emitter layer (2), the p ＋ polysilicon layer (6) is arranged on the first tunneling oxide layer (5), and the Ag / Al electrode (7) is arranged on the p ＋ polysilicon layer (6); silicon nitride anti-reflection layer (4), which is arranged on the aluminum oxide passivation layer (3); n ＋ a polysilicon layer (9);n ＋ The polysilicon layer (9) is arranged on the bottom surface of the second tunneling oxide layer (8);n ＋ The bottom surface of the polysilicon layer (9) is provided with at least one convex end (10); Silicon nitride passivation layer (11); silicon nitride passivation layer (11) laid in n ＋ Polycrystalline silicon layer (9) bottom surface, silicon nitride passivation layer (11) covers the convex end (10); second tunneling oxide layer (8), which is arranged on the bottom surface of the n-type crystalline silicon substrate (1); 2. The TOPCon solar cell with a selectively passivated contact structure according to claim 1, characterized in that, at least one Ag electrode (12), which is connected with a protruding end (10) through the silicon nitride passivation layer (11).

3. The TOPCon solar cell with a selectively passivated contact structure according to claim 1, characterized in that, The n-type crystalline silicon substrate (1) is an n-type Cz single-crystal silicon wafer with an emitter sheet resistance of 120-140 ohm / square, a junction depth of 0.8-1.2 microns, a thickness of 120-150 microns, a resistivity of 0.5-2 ohm*cm and a crystal orientation of (100).

4. The TOPCon solar cell with a selectively passivated contact structure according to claim 1, characterized in that, The thicknesses of the aluminum oxide passivation layer (3) and the silicon nitride anti-reflection layer (4) are 3-5 nm and 70-80 nm respectively.

5. The TOPCon solar cell with a selectively passivated contact structure according to claim 1, characterized in that, The thicknesses of the first tunneling oxide layer (5) and the second tunneling oxide layer (8) are both 1-2 nm, and the first tunneling oxide layer (5) and the second tunneling oxide layer (8) are both formed by depositing silicon oxide. The thickness of the silicon nitride passivation layer (11) is 90-120 nm.

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