TOPCon solar cell structure

Abstract

The utility model discloses a TOPCon solar cell structure, which relates to the field of solar cells and sequentially comprises a first silver electrode, a first antireflection film layer, a boron doping layer, a silicon substrate, a tunneling layer and a polycrystalline silicon doping layer in a single direction, and further comprises a second antireflection film layer, a diffusion barrier layer and a second silver electrode. One grid line of the diffusion barrier layer is arranged between two adjacent grid lines of the second antireflection film layer, and the grid line of the second silver electrode is located on the grid line of the diffusion barrier layer; a titanium nitride layer TiN or a titanium oxynitride layer TiON is deposited between the polycrystalline silicon layer and the metal electrode to serve as a diffusion barrier layer, and the second silver electrode is of a grid line structure instead of full coverage; according to the structure, the characteristics of high conductivity and electron selective transmission of titanium nitride or titanium oxynitride are utilized, so that electrons have low resistance during transmission, and electron collection is facilitated. And by adopting a grid line structure, the absorption of titanium nitride or titanium oxynitride on long-wave-band light is effectively avoided, and the double-sided topcon battery is very suitable for the existing double-sided topcon battery.

Description

Technical Field

[0001] The utility model relates to the field of solar cells, in particular to a TOPCon solar cell structure. Background Art

[0002] Currently, high-efficiency and low-cost solar cells are of great significance to the development of new energy.

[0003] Among many types of solar cells, TOPCon solar cells have high photoelectric conversion efficiency, which is very close to the theoretical efficiency of silicon-based solar cells. At the same time, the TOPCon solar cell production line can be easily improved from the previous PERC cell production line. Therefore, the development of TOPCon solar cells is very promising.

[0004] At present, TOPCon solar cells are still far from the theoretical efficiency, and the contact problem between the metal electrode and the battery is one of the reasons for reducing the performance of the battery. The main reason is that the contact between the metal electrode and the polysilicon layer on the back of the battery will produce contact resistance. In the existing technology, increasing the doping concentration in the polysilicon layer can improve the contact between the polysilicon layer and the metal electrode, but too high a doping concentration will damage the silicon oxide layer and have a deeper junction depth, which is a bad result and will reduce the performance of the battery. There is a technology that mentions the use of two stacked polysilicon layers with different concentrations. In order to avoid the doping concentration of the two polysilicon layers tending to be consistent during high-temperature annealing, a silicon oxide barrier layer is added between the two layers to block the diffusion of doped phosphorus, thereby avoiding the doping concentration tending to be consistent. However, since the silicon oxide layer is insulating, this method improves the contact between the polysilicon and the metal electrode, but also increases the body resistance. Utility Model Content

[0005] The purpose of the utility model is to design a TOPCon solar cell structure in order to solve the above problems.

[0006] The utility model achieves the above-mentioned purpose through the following technical solutions:

[0007] A TOPCon solar cell structure comprises, in sequence from a single direction, a first silver electrode, a first anti-reflection film layer, a boron-doped layer, a silicon substrate, a tunneling layer and a polysilicon-doped layer. The TOPCon solar cell structure also comprises a second anti-reflection film layer, a diffusion barrier layer and a second silver electrode. The second anti-reflection film layer, the diffusion barrier layer and the second silver electrode are all gate line structures. The second anti-reflection film layer and the diffusion barrier layer are both located on a side of the polysilicon-doped layer away from the tunneling layer. A gate line of the diffusion barrier layer is located between two adjacent gate lines of the second anti-reflection film layer. The gate line of the second silver electrode is located on the gate line of the diffusion barrier layer. The diffusion barrier layer is made of TiN or TiON.

[0008] The beneficial effect of the utility model is that a titanium nitride layer TiN or a titanium oxynitride layer TiON is deposited between the polysilicon layer and the metal electrode as a diffusion barrier layer, and the second silver electrode is a grid line structure, rather than full coverage; this structure utilizes the high conductivity and electron selective transmission characteristics of titanium nitride or titanium oxynitride, so that electrons have low resistance during transmission, which is conducive to electron collection. The grid line structure effectively avoids the absorption of long-wavelength light by titanium nitride or titanium oxynitride, and is very suitable for existing double-sided topcon cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the structure of a TOPCon solar cell structure of the utility model;

[0010] The corresponding figures are as follows:

[0011] 1-first silver electrode, 2-first anti-reflection film layer, 3-boron doped layer, 4-silicon substrate, 5-tunneling layer, 6-polysilicon doped layer, 7-second anti-reflection film layer, 8-diffusion barrier layer, 9-second silver electrode. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0013] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0015] In the description of the present utility model, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the utility model product is usually placed when in use, or are directions or positional relationships that are usually understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present utility model.

[0016] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0017] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] The specific implementation of the utility model is described in detail below in conjunction with the accompanying drawings.

[0019] like Figure 1 As shown, a TOPCon solar cell structure includes, from a single direction, a first silver electrode 1, a first anti-reflection film layer 2, a boron-doped layer 3, a silicon substrate 4, a tunneling layer 5 and a polysilicon doped layer 6 in sequence. The TOPCon solar cell structure also includes a second anti-reflection film layer 7, a diffusion barrier layer 8 and a second silver electrode 9; the second anti-reflection film layer 7, the diffusion barrier layer 8 and the second silver electrode 9 are all gate line structures, the second anti-reflection film layer 7 and the diffusion barrier layer 8 are both located on the side of the polysilicon doped layer 6 away from the tunneling layer 5, a gate line of the diffusion barrier layer 8 is between two adjacent gate lines of the second anti-reflection film layer 7, the gate line of the second silver electrode 9 is located on the gate line of the diffusion barrier layer 8, and the diffusion barrier layer 8 is made of TiN or TiON.

[0020] The thickness of the diffusion barrier layer 8 is in the range of 10-100 nm.

[0021] The first anti-reflection film layer 2 and the second anti-reflection film layer 7 are both made of silicon nitride, and the thickness of the first anti-reflection film layer 2 and the second anti-reflection film layer 7 is in the range of 60-100 nm.

[0022] The first anti-reflection film layer 2 is a silicon nitride layer or an aluminum oxide layer, the tunneling layer 5 is a silicon oxide layer, the second anti-reflection film layer 7 is a silicon oxide layer, and the diffusion barrier layer 8 is a titanium nitride layer TiN or a titanium oxynitride layer TiON.

[0023] A titanium nitride layer TiN or titanium oxynitride layer TiON is deposited between the polysilicon layer and the metal electrode as a diffusion barrier layer 8, and the second silver electrode 9 is a grid line structure instead of full coverage; this structure utilizes the high conductivity and electron selective transmission characteristics of titanium nitride or titanium oxynitride, so that electrons have low resistance during transmission, which is conducive to electron collection. The grid line structure effectively avoids the absorption of long-wavelength light by titanium nitride or titanium oxynitride, which is very suitable for existing double-sided topcon cells.

[0024] The manufacturing process of a TOPCon solar cell structure of the utility model is as follows:

[0025] 1) The original N-type silicon wafer undergoes a texturing process and double-sided texturing to form a pyramid-shaped velvet surface;

[0026] 2) After the silicon wafer is textured, it goes through a laser process to carve laser grooves under the front gate line.

[0027] 3) Boron diffusion is carried out in a high-temperature diffusion furnace to form a P-type semiconductor on the front side, forming a PN junction with a square resistance range of 320-450 ohms;

[0028] 4) The chain cleaning machine cleans the BSG on the back, and the tank machine polishes the back;

[0029] 6) Generate a tunneling layer 5 and a polysilicon doped layer 6 on the back side by PECVD. The deposition film thickness ranges from 70 to 150 nm;

[0030] 7) Use high temperature tubular annealing furnace to activate doping atoms and improve crystallization rate. Sheet resistance range is 20-60 ohms;

[0031] 8) Use a chain cleaning machine and a tank cleaning machine to remove the front side expansion and mask layer.

[0032] 9) Use ALD equipment to deposit 2-7nm aluminum oxide on the front.

[0033] 10) Deposit the first anti-reflection film layer 2 of silicon nitride on the front side by PECVD. The film thickness is 60-100 nm.

[0034] 11) Deposit the second anti-reflection film layer 7 of silicon nitride on the back by PECVD. The film thickness is 60-100 nm. A mask is used when depositing silicon nitride on the back.

[0035] 12) Magnetron sputtering deposition (TiN / TiON) is used, using a mask, and the deposition thickness ranges from 10 to 100 nm.

[0036] 13) Screen print silver paste on the front and back sides to form front and back metal grid lines to transmit current.

[0037] 14) Finally, an ohmic contact is formed through light injection equipment and laser sintering technology.

[0038] Test the efficiency of the battery cell.

[0039] The back side adopts SiO2 / poly / (TiN or TiON) / Ag structure; the polysilicon poly layer itself only needs to ensure the passivation effect, and there is no need to increase the doping concentration (the doping concentration is equivalent to the electron concentration). (TiN or TiON) has the characteristics of high electron concentration and low work function, which plays a role in improving contact; (TiN or TiON) can also serve as a diffusion barrier layer 8 for Ag to prevent Ag from diffusing into the polysilicon layer.

[0040] The back electrode part, namely (TiN or TiON) / Ag, is a grid line structure; the grid line structure is suitable for the double-sided solar cell structure type on the one hand, and on the other hand, it greatly reduces the absorption of strong long-wave light by (TiN or TiON).

[0041] After preparing the polysilicon layer, use a mask to deposit silicon nitride, leaving a position for deposition (TiN or TiON), and then use the mask for deposition (TiN or TiON) to block the silicon nitride and only deposit (TiN or TiON) at the designated position. Finally, use the screen with the same structure as the deposition (TiN or TiON) to prepare the Ag gate line.

[0042] The preparation methods of (TiN or TiON) include but are not limited to magnetron sputtering coating and electron beam evaporation coating.

[0043] The technical solution of the present utility model is not limited to the above-mentioned specific embodiments, and all technical variations made according to the technical solution of the present utility model fall within the protection scope of the present utility model.

Claims

1. A TOPCon solar cell structure, comprising, in sequence from a single direction, a first silver electrode, a first anti-reflection film layer, a boron-doped layer, a silicon substrate, a tunneling layer and a polysilicon-doped layer, characterized in that: The TOPCon solar cell structure also includes a second anti-reflection film layer, a diffusion barrier layer and a second silver electrode; the second anti-reflection film layer, the diffusion barrier layer and the second silver electrode are all gate line structures, the second anti-reflection film layer and the diffusion barrier layer are both located on the side of the polysilicon doped layer away from the tunneling layer, a gate line of the diffusion barrier layer is between two adjacent gate lines of the second anti-reflection film layer, the gate line of the second silver electrode is located on the gate line of the diffusion barrier layer, and the diffusion barrier layer is made of TiN or TiON.

2. A TOPCon solar cell structure according to claim 1, characterized in that: The thickness of the diffusion barrier layer is in the range of 10-100 nm.

3. A TOPCon solar cell structure according to claim 1, characterized in that: The first anti-reflection film layer and the second anti-reflection film layer are both made of silicon nitride, and the thickness of the first anti-reflection film layer and the second anti-reflection film layer ranges from 60 to 100 nm.

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