Novel TOPCon battery structure and photovoltaic module thereof

Abstract

The utility model discloses a novel TOPCon cell structure and a photovoltaic assembly thereof, which belong to the technical field of solar cells, and comprise an N-type silicon substrate, the front surface of the N-type silicon substrate is sequentially provided with a front surface suede, a boron diffusion layer, a first front surface passivation layer, a second front surface passivation layer and a front surface conductive metal electrode from inside to outside, the back surface of the N-type silicon substrate comprises a metal region and a non-metal region which are of a planar structure, and the metal region is sequentially provided with a back surface tunneling oxide layer, a phosphorus-doped polycrystalline silicon layer, a first back surface passivation layer, a second back surface passivation layer and a back surface conductive metal electrode from inside to outside; the non-metal area is sequentially provided with a back suede, a first back passivation layer and a second back passivation layer from inside to outside. The technology of removing the superposed polycrystalline silicon layer in the back non-metallization area and growing the suede reduces the optical parasitic absorption of the polycrystalline silicon layer, increases the light absorption of the back of the cell, and effectively improves the double-sided rate of the cell.

Description

TECHNICAL FIELD

[0001] The utility model belongs to solar cell technical field, concretely relates to a novel TOPCon cell structure and photovoltaic module thereof. BACKGROUND

[0002] TOPCon is N type silicon substrate cell, generally boron doped P+ layer is formed on the front surface, and phosphorus doped N++ layer is formed on the back surface. The silicon substrate structure mainly has two kinds, wherein the first kind is front surface roughening and back surface polishing, and a layer of ultra-thin silicon oxide is prepared on the polishing surface, and then a layer of thick phosphorus-doped polysilicon layer is deposited, and the two together form a passivation contact structure. The polishing surface has poor light absorption capacity, and the thick phosphorus-doped polysilicon layer has strong parasitic absorption, which makes the double-side rate of the cell under this structure low. The second kind is double-side roughening, which can improve the back surface light absorption capacity, but the interface passivation effect of the roughening and the passivation contact structure composed of the tunneling oxide layer and the phosphorus-doped polysilicon is poor, resulting in low back surface efficiency, which makes it difficult to improve the double-side rate of the cell under this structure.

[0003] The existing technology for the above two structures has been optimized. The first kind is to thin the polysilicon layer thickness of the non-metallized area on the back surface of TOPCon by laser opening film technology. For example, in the invention patent CN118380508A, the position of the non-metallized area on the back surface of the silicon wafer is treated by laser, the phosphor silicon glass layer on the surface of the phosphorus-doped polysilicon layer in this area is removed or modified into a loose structure, and the residual phosphorus-doped polysilicon layer and back surface tunneling oxide layer in the non-metallized area irradiated by laser are removed by alkali washing. The second kind adopts double-side roughening structure to form uneven pyramid roughening on the surface of the silicon wafer, which increases the light absorption. For example, in the invention patent CN111477719A, double-side roughening is prepared, and the preparation of the cell wafer is completed through subsequent boron / phosphorus diffusion and cleaning, passivation and other steps. The back surface roughening increases the light absorption capacity, which is beneficial to improve the double-side rate of the cell.

[0004] In order to reduce the parasitic absorption problem of the thick phosphorus-doped polysilicon layer on the back surface, laser is used to thin or remove the non-metallized area, which can reduce the parasitic absorption of the thick polysilicon layer while ensuring the passivation and contact performance of the back surface. However, the back surface of the silicon substrate is a polishing surface with weak light absorption capacity, which makes the double-side rate of the cell low and difficult to improve. Although double-side roughening can improve the light absorption capacity of the back surface of the silicon substrate and improve the double-side rate, the interface passivation between the roughening and the passivation structure composed of the tunneling oxide layer and the phosphorus-doped polysilicon layer is poor, and the passivation and contact performance cannot achieve the expected effect.

[0005] In view of this, the present inventors have carried out in-depth research on this demand, and thus the present case is produced. CONTENT OF THE UTILITY MODEL

[0006] To overcome the above-mentioned technical problems of weak light absorption ability of the back surface of the silicon substrate as a polished surface, poor interface passivation between the textured surface and the passivation structure composed of the tunneling oxide layer and the phosphorus-doped polysilicon layer, and low silicon wafer double-sided rate, the utility model provides a novel TOPCon cell structure, including N type silicon substrate, the front surface of the N type silicon substrate is sequentially provided with front surface texture, boron diffusion layer, first front surface passivation layer, second front surface passivation layer and front surface conductive metal electrode from inside to outside, the back surface of the N type silicon substrate includes the metal area and the nonmetal area of plane structure, the metal area is sequentially provided with back surface tunneling oxide layer, phosphorus-doped polysilicon layer, first back surface passivation layer, second back surface passivation layer and back surface conductive metal electrode from inside to outside, the nonmetal area is sequentially provided with back surface texture, first back surface passivation layer, second back surface passivation layer from inside to outside;

[0007] The front surface conductive metal electrode forms ohmic contact with the boron diffusion layer through the first front surface passivation layer and the second front surface passivation layer, and the back surface conductive metal electrode forms ohmic contact with the phosphorus-doped polysilicon layer through the first back surface passivation layer and the second back surface passivation layer.

[0008] Further, the phosphorus-doped polysilicon layer is arranged close to the back surface tunneling oxide layer, and the thickness of the phosphorus-doped polysilicon layer is 100-300 nm, wherein the concentration of phosphorus during phosphorus doping is 1×10 19 cm -3 -5×10 20 cm -3 .

[0009] Further, the sheet resistance of the boron diffusion layer is 100-300 Ω / m, and pure hydrogen and diborane are used as boron precursors for doping.

[0010] Further, the nonmetal area of the back surface of the N type silicon substrate is a pyramid texture, and the size of the pyramid texture is 8-12 μm.

[0011] Further, the first front surface passivation layer and the second front surface passivation layer are Al2O3 thin film layer and SiNx thin film layer respectively, and the first back surface passivation layer and the second back surface passivation layer are both SiNx thin film layer.

[0012] Further, the N type silicon substrate is a phosphorus-doped N type silicon substrate, and the resistivity is 0.1-10.0 Ω / cm, and the thickness is 120-180 um.

[0013] Further, the thickness of the back surface tunneling oxide layer is 1-3 nm, and the width of the front surface conductive metal electrode is 30-120 mm.

[0014] Further, the front conductive metal electrode is an Ag / Al grid electrode, and the back conductive metal electrode is an Ag grid electrode.

[0015] Further, the first front passivation layer, the second front passivation layer, the first back passivation layer and the second back passivation layer are all aluminum oxide with a thickness of 2-6nm and are obtained by ALD deposition.

[0016] The utility model discloses still provide a kind of photovoltaic module, including cover plate, encapsulating material layer, solar cell string, the solar cell string includes multiple as above-mentioned novel TOPCon cell structure.

[0017] The beneficial effects of the technical scheme of the utility model are as follows:

[0018] (1) the back surface uses doped polysilicon passivation contact, avoids the metal contact recombination caused by the direct contact of the front conductive metal electrode of the TOPCon cell and the emitter doped layer, and improves the bifaciality of the cell.

[0019] (2) for the bifaciality of the N-type TOPCon cell is low to ensure sufficient passivation performance, combined with laser opening film and wet process, remove N+poly and tunneling oxide layer in the non-laser area of the cell back surface, and form a textured surface in the area by etching, which improves the bifaciality of the cell while ensuring the passivation performance of the N-type TOPCon cell.

[0020] (3) the utility model discloses a novel TOPCon cell structure, which is characterized by the following technical scheme: a silicon substrate is provided, and a passivation layer is formed on the front surface of the silicon substrate. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical scheme of the embodiments of the utility model, the following will be briefly introduced to the drawings needed to be used in the embodiments, it should be understood that the following drawings only show some embodiments of the utility model, therefore should not be regarded as the limitation to the scope, for ordinary skilled person in the art, under the premise of not paying the creative labor, can also obtain other related drawings according to these drawings.

[0022] Figure 1 is a structure diagram of a novel TOPCon cell structure of the utility model;

[0023] In the figure, 1, N-type silicon substrate; 2, front surface roughness; 3, boron diffusion layer; 4, first front surface passivation layer; 5, second front surface passivation layer; 6, front surface conductive metal electrode; 7, metal area; 8, non-metal area; 9, back surface tunneling oxide layer; 10, phosphorus doped polysilicon layer; 11, first back surface passivation layer; 12, second back surface passivation layer; 13, back surface conductive metal electrode; 14, back surface roughness. DETAILED DESCRIPTION

[0024] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0025] The back surface of the present embodiment adopts doped polysilicon passivation contact, avoiding the metal contact recombination caused by the direct contact between the back surface metal electrode of the TOPCon cell and the emitter doped layer, and improving the double-sided rate of the cell. The specific implementation is as follows:

[0026] As shown in Figure 1 A novel TOPCon cell structure includes an N-type silicon substrate 1, the front surface of the N-type silicon substrate 1 is sequentially provided from inside to outside with a front surface roughness 2, a boron diffusion layer 3, a first front surface passivation layer 4, a second front surface passivation layer 5 and a front surface conductive metal electrode 6, the back surface of the N-type silicon substrate 1 includes a metal area 7 and a non-metal area 8 in a planar structure, the metal area 7 is sequentially provided from inside to outside with a back surface tunneling oxide layer 9, a phosphorus doped polysilicon layer 10, a first back surface passivation layer 11, a second back surface passivation layer 12 and a back surface conductive metal electrode 13, and the non-metal area 8 is sequentially provided from inside to outside with a back surface roughness 14, the first back surface passivation layer 11 and the second back surface passivation layer 12.

[0027] The front surface conductive metal electrode 6 forms an ohmic contact with the boron diffusion layer 3 through the first front surface passivation layer 4 and the second front surface passivation layer 5; and the back surface conductive metal electrode 13 forms an ohmic contact with the phosphorus doped polysilicon layer 10 through the first back surface passivation layer 11 and the second back surface passivation layer 12.

[0028] As a preferred embodiment, the phosphorus-doped polysilicon layer 10 is arranged close to the back tunnel oxide layer 9, the thickness of the phosphorus-doped polysilicon layer 10 is 100-300 nm, and the concentration of phosphorus in the phosphorus-doped polysilicon layer 10 is 1x10 19 cm -3 -5x10 20 cm -3 .

[0029] As a preferred embodiment, the sheet resistance of the boron diffusion layer 3 is 100-300 Ω / m, and pure hydrogen and diborane are used as boron precursors for doping.

[0030] As a preferred embodiment, the non-metallic region 8 on the back of the N-type silicon substrate 1 is a pyramid texture with a pyramid texture size of 8-12 μm.

[0031] As a preferred embodiment, the first front passivation layer 4 and the second front passivation layer 5 are Al2O3 thin film layers and SiNx thin film layers, respectively, and the first back passivation layer 11 and the second back passivation layer 12 are both SiNx thin film layers.

[0032] As a preferred embodiment, the N-type silicon substrate 1 is a phosphorus-doped N-type silicon substrate 1 with a resistivity of 0.1-10.0 Ω / cm and a thickness of 120-180 μm.

[0033] As a preferred embodiment, the thickness of the back tunnel oxide layer 9 is 1-3 nm, and the width of the front conductive metal electrode 6 is 30-120 mm.

[0034] As a preferred embodiment, the front conductive metal electrode 6 is an Ag / Al grid electrode, and the back conductive metal electrode 13 is an Ag grid electrode.

[0035] As a preferred embodiment, the first front passivation layer 4, the second front passivation layer 5, the first back passivation layer 11, and the second back passivation layer 12 are all aluminum oxide with a thickness of 2-6 nm, and are obtained by ALD deposition.

[0036] The present embodiment also provides a photovoltaic module, which comprises a cover plate, an encapsulating material layer, and a solar cell string, wherein the solar cell string comprises a plurality of novel TOPCon cell structures as described above.

[0037] Embodiment 1

[0038] The present embodiment provides a preparation process of a novel TOPCon cell structure, which comprises the following steps:

[0039] S1: Double-sided texturing is performed on an N-type silicon substrate, boron diffusion is performed on the front surface of the textured silicon substrate to form a P+ emitter layer and BSG; and alkaline polishing is performed on the back surface of the silicon substrate to form a polished surface;

[0040] S2: A tunnel oxide layer and a phosphorus-doped polysilicon layer are sequentially deposited on the polished surface by LPCVD, the thickness of the tunnel oxide layer is 1 nm, the thickness of the polysilicon layer is 50 nm, phosphorus doping is performed on the deposited polysilicon layer to form a phosphorus-doped polysilicon layer, and the concentration of the phosphorus-doped polysilicon layer is 1×10 19 cm -3 , and a layer of PSG is formed on the surface;

[0041] S3: The back surface of the N-type silicon substrate is scanned by laser in a non-metallized area to remove the phosphosilicate glass (PSG) on the surface of the phosphorus-doped polysilicon layer in the area, and the bottom phosphorus-doped polysilicon layer is exposed; the metallized area not subjected to laser treatment retains the phosphorus-doped polysilicon layer and the tunnel oxide layer; wherein the laser parameters are: laser wavelength 300 nm, frequency 500 kHz, scanning speed 10 m / s, and spot size > 200 μm;

[0042] S4: Chain acid washing is used to remove the phosphosilicate glass (PSG) on the front surface and the side surface, and to expose the polysilicon layer on the winding surface;

[0043] S5: Slot alkali washing is used to remove the phosphorus-doped polysilicon layer on the front surface and the side surface, and to remove the residual phosphorus-doped polysilicon and tunnel oxide layer in the non-metallized area after the laser process on the back surface, and to etch back to the silicon substrate; the silicon substrate in this area is etched by the alkali solution to form a textured surface. The concentration of the alkali solution used is 3%, and the treatment time is 400 s;

[0044] S6: Slot acid washing is used to remove the BSG on the front surface of the silicon wafer and the PSG in the metallized area on the back surface, and to remove the residual tunnel oxide layer in the non-metallized area on the back surface;

[0045] S7: ALOX layer is deposited on the front surface of the silicon wafer after the process by ALD, SiNx layer is deposited on the back surface by PECVD;

[0046] S8: Metal electrodes are printed on the front and back metallized areas of the cell structure formed by S6 by screen printing.

[0047] Example 2

[0048] The present embodiment provides a preparation process of a new TOPCon cell structure, comprising the following steps:

[0049] S1: Double-sided texturing is performed on an N-type silicon substrate, boron diffusion is performed on the front surface of the textured silicon substrate to form a P+ emitter layer and BSG; and alkaline polishing is performed on the back surface of the silicon substrate to form a polished surface;

[0050] S2: LPCVD is used to deposit a tunnel oxide layer and a phosphorus-doped polysilicon layer on the polished surface in sequence, the thickness of the tunnel oxide layer is 3 nm, the thickness of the polysilicon layer is 200 nm, phosphorus doping is performed on the deposited polysilicon layer to form a phosphorus-doped polysilicon layer, and the concentration is 5*10 20 cm -3 , and a layer of PSG is formed on the surface;

[0051] S3: The non-metallized area on the back surface of the N-type silicon substrate is scanned by laser to remove the phosphosilicate glass (PSG) on the surface of the phosphorus-doped polysilicon layer in the area, and the bottom phosphorus-doped polysilicon layer is exposed, and the metallized area not subjected to laser treatment retains the phosphorus-doped polysilicon layer and the tunnel oxide layer; wherein the laser parameters are: laser wavelength 1100 nm, frequency 1000 kHz, scanning speed 200 m / s, and spot size > 200 μm;

[0052] S4: Chain acid washing is used to remove the phosphosilicate glass (PSG) on the front and side surfaces, and expose the polysilicon layer on the winding;

[0053] S5: Slot alkali washing is used to remove the phosphorus-doped polysilicon layer on the front and side surfaces, and at the same time, remove the residual phosphorus-doped polysilicon and tunnel oxide layer in the non-metallized area on the back surface after the laser process, and etch back to the silicon substrate, and the silicon substrate in the area forms a textured surface under the etching of the alkali solution. The concentration of the alkali solution used is 60%, and the treatment time is 800 s;

[0054] S6: Slot acid washing is used to remove the BSG on the front surface of the silicon wafer and the PSG on the back surface of the metallized area, and the residual tunnel oxide layer in the non-metallized area on the back surface;

[0055] S7: ALOX layer is deposited on the front surface of the silicon wafer after the process in sequence by ALD, SiNx layer is deposited on the back surface by PECVD;

[0056] S8: Metal electrodes are printed on the front and back metallized areas of the cell structure formed after S6 by screen printing.

[0057] Example 3

[0058] The embodiment provides a preparation process of a new TOPCon cell structure, including the following steps:

[0059] S1: The N-type silicon substrate is subjected to double-sided texturing, boron diffusion is performed on the front surface of the silicon substrate to form a P+ emitter layer and BSG, and the back surface of the silicon substrate is subjected to alkali polishing to form a polished surface;

[0060] S2: on the polished surface, a tunneling oxide layer and a phosphorus-doped polysilicon layer are deposited in sequence by LPCVD, wherein the thickness of the tunneling oxide layer is 2 nm, the thickness of the polysilicon layer is 150 nm, phosphorus doping is performed on the deposited polysilicon layer to form a phosphorus-doped polysilicon layer, and the concentration is 3*1019 / cm2, and a layer of PSG is formed on the surface; 20 cm -3 , and a layer of PSG is formed on the surface;

[0061] S3: the non-metallized area on the back surface of the N-type silicon substrate is scanned by laser to remove the phosphor silicon glass (PSG) on the surface of the phosphorus-doped polysilicon layer in the area, and the bottom phosphorus-doped polysilicon layer is exposed, and the metallized area not subjected to laser treatment retains the phosphorus-doped polysilicon layer and the tunneling oxide layer; wherein the laser parameters are: laser wavelength 700 nm, frequency 800 kHz, scanning speed 100 m / s, and spot size > 200 μm;

[0062] S4: chain acid washing is used to remove the phosphor silicon glass (PSG) on the front surface and the side surface, and expose the polysilicon layer of the winding degree;

[0063] S5: groove alkali washing is used to remove the phosphorus-doped polysilicon layer on the front surface and the side surface, and at the same time, remove the residual phosphorus-doped polysilicon and tunneling oxide layer in the non-metallized area on the back surface after the laser process, and etch back to the silicon substrate, and the silicon substrate in the area forms a textured surface under the etching of the alkali solution; wherein the concentration of the alkali solution is 30%, and the processing time is 600 s;

[0064] S6: groove acid washing is used to remove the BSG on the front surface of the silicon wafer and the PSG in the metallized area on the back surface, and the residual tunneling oxide layer in the non-metallized area on the back surface;

[0065] S7: ALOX layer is deposited on the front surface of the silicon wafer after the process in sequence by ALD, SiNx layer is deposited on the back surface by PECVD;

[0066] S8: metal electrodes are printed on the front surface and the back surface metallized area of the cell structure formed by S6 by screen printing.

[0067] The above is only a preferred embodiment of the present application, and is not used to limit the present application. For those skilled in the art, the present application can be variously changed and modified. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A novel TOPCon cell structure, characterized in that, The N-type silicon substrate (1) is provided with, from inside to outside, a front surface rough surface (2), a boron diffusion layer (3), a first front surface passivation layer (4), a second front surface passivation layer (5) and a front surface conductive metal electrode (6) on the front surface; the back surface of the N-type silicon substrate (1) comprises a planar structure of a metal region (7) and a non-metal region (8), the metal region (7) is provided with, from inside to outside, a back surface tunneling oxide layer (9), a phosphorus-doped polysilicon layer (10), a first back surface passivation layer (11), a second back surface passivation layer (12) and a back surface conductive metal electrode (13), and the non-metal region (8) is provided with, from inside to outside, a back surface rough surface (14), the first back surface passivation layer (11) and the second back surface passivation layer (12). The front surface conductive metal electrode (6) forms an ohmic contact with the boron diffusion layer (3) through the first front surface passivation layer (4) and the second front surface passivation layer (5); and the back surface conductive metal electrode (13) forms an ohmic contact with the phosphorus-doped polysilicon layer (10) through the first back surface passivation layer (11) and the second back surface passivation layer (12).

2. A novel TOPCon cell structure according to claim 1, characterized in that, The phosphorus-doped polysilicon layer (10) is arranged close to the back tunnel oxide layer (9), the thickness of the phosphorus-doped polysilicon layer (10) is 100-300 nm, wherein the concentration of phosphorus during phosphorus doping is 1 x 10 19 cm -3 -5 x 10 20 cm -3 .

3. A novel TOPCon cell structure according to claim 1, characterized in that, The sheet resistance of the boron diffusion layer (3) is 100-300Ω / m, and pure hydrogen and diborane are used as boron precursors for doping.

4. The novel TOPCon cell structure of claim 1, wherein, The non-metal region (8) of the back surface of the N-type silicon substrate (1) is a pyramid rough surface, and the size of the pyramid rough surface is 8-12μm.

5. The novel TOPCon cell structure according to claim 1, characterized in that, The first front surface passivation layer (4) and the second front surface passivation layer (5) are Al2O3 thin film layers and SiNx thin film layers, respectively; and the first back surface passivation layer (11) and the second back surface passivation layer (12) are SiNx thin film layers.

6. The novel TOPCon cell structure according to claim 1, characterized in that, The N-type silicon substrate (1) is a phosphorus-doped N-type silicon substrate (1) with a resistivity of 0.1-10.0Ω / cm and a thickness of 120-180μm.

7. The novel TOPCon cell structure according to claim 1, characterized in that, The thickness of the back surface tunneling oxide layer (9) is 1-3nm, and the width of the front surface conductive metal electrode (6) is 30-120mm.

8. A novel TOPCon cell structure according to claim 1, characterized in that, The front surface conductive metal electrode (6) is an Ag / Al gate line electrode, and the back surface conductive metal electrode (13) is an Ag gate line electrode.

9. A novel TOPCon cell structure according to claim 1, characterized in that, The first front surface passivation layer (4), the second front surface passivation layer (5), the first back surface passivation layer (11) and the second back surface passivation layer (12) are all aluminum oxide with a thickness of 2-6nm and are obtained by ALD deposition.

10. A photovoltaic module, characterized by, The cover plate, the encapsulating material layer and the solar cell string are provided, and the solar cell string comprises a plurality of novel TOPCon cell structures according to any one of claims 1-9.

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