Preparation method of heterojunction solar cell composite TCO

Abstract

The invention discloses a preparation method of a heterojunction solar cell composite TCO, and the method comprises the steps: selecting an N-type silicon wafer as a silicon substrate, and processing the N-type silicon wafer to obtain a textured surface with two pyramid-shaped surfaces; adopting PECVD (Plasma Enhanced Chemical Vapor Deposition) to sequentially deposit a front intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer on the front suede; sequentially depositing a back intrinsic amorphous silicon layer and a P-type doped amorphous silicon layer on the back suede; depositing a first transparent conductive layer, a second transparent conductive layer and a metal conductive layer on the P-type doped amorphous silicon layer; depositing a third transparent conductive layer, a fourth transparent conductive layer and a fifth transparent conductive layer on the N-type doped amorphous silicon layer; printing a back grid line on the metal conductive layer, and printing a front grid line on the fifth transparent conductive layer; the laminated layer has the photoelectric characteristic similar to that of ITO, the electrical conductivity of the metal film is good, the metal film can replace part of silver paste to transmit electrons, and the consumption of silver is reduced while the consumption of indium is reduced.

Description

Technical Field

[0001] The invention relates to the field of solar cell manufacturing, in particular to a method for preparing a heterojunction solar cell composite TCO. Background Art

[0002] With the development of heterojunction solar cells, reducing the cost of battery manufacturing has become a focus of attention. Indium tin oxide (ITO) is often used in the transparent conductive film layer. ITO has the characteristics of high transmittance, low resistivity and excellent performance. However, due to the scarcity and high price of indium, its cost is relatively high, which limits the development of ITO in future heterojunction batteries. Therefore, less indium or no indium in the transparent conductive film layer has become an important direction for reducing the cost of heterojunction batteries. In addition, the silver consumption of the conductive paste of heterojunction batteries is more than that of other types of silicon-based batteries. Reducing silver consumption has become another important direction for reducing the cost of heterojunction batteries.

[0003] Compared with ITO, Al-doped zinc oxide (AZO) transparent conductive film has the advantages of abundant raw materials and low price. At present, the price of metal Zn and Al is about 1% of metal In and 10% of metal tin. In addition, AZO has good thermal stability and is not easy to lose oxygen during heat treatment (relative to ITO). Therefore, AZO film has replaced ITO film and has become an important research direction. However, the resistivity of AZO film is slightly worse, resulting in poor contact characteristics with semiconductor silicon, and AZO has poor acid and alkali resistance and atmospheric weather resistance. The static resistivity will increase in the atmospheric environment. These factors affect the application of AZO film in heterojunction batteries. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a composite TCO of a heterojunction solar cell, which can not only ensure the light transmittance requirement of the front side but also meet the atmospheric weather resistance of the transparent conductive film on the front side of the cell and good contact with semiconductor silicon.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] A method for preparing a composite TCO of a heterojunction solar cell comprises the following steps: selecting an N-type silicon wafer as a silicon substrate, cleaning and texturing the wafer to obtain a pyramid-shaped textured surface on both sides; one side of the N-type silicon wafer is referred to as the front side, and the other side is referred to as the back side; using PECVD to sequentially deposit a front intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer on the front textured surface; and sequentially depositing a back intrinsic amorphous silicon layer and a P-type doped amorphous silicon layer on the back textured surface;

[0007] Depositing a first transparent conductive layer on the P-type doped amorphous silicon layer, depositing a second transparent conductive layer on the first transparent conductive layer, and depositing a metal conductive layer on the second transparent conductive layer;

[0008] Depositing a third transparent conductive layer on the N-type doped amorphous silicon layer, depositing a fourth transparent conductive layer on the third transparent conductive layer, and depositing a fifth transparent conductive layer on the fourth transparent conductive layer;

[0009] The back grid lines are printed on the metal conductive layer, and the front grid lines are printed on the fifth transparent conductive layer.

[0010] Preferably, the first transparent conductive layer is ITO, and the first transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

[0011] Preferably, the second transparent conductive layer is AZO, and the second transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

[0012] Preferably, the metal conductive layer is a highly conductive copper film, which is deposited by magnetron sputtering and has a thickness of 200-500 nm.

[0013] Preferably, the third transparent conductive layer is ITO, and the third transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

[0014] Preferably, the fourth transparent conductive layer is AZO, and the fourth transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

[0015] Preferably, the fifth transparent conductive layer is ITO, and the fifth transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are:

[0017] Currently, the TCO film layer uses an ITO transparent conductive film, but the In element resource is scarce and expensive. The present invention can significantly reduce the amount of indium used, and the laminate has similar photoelectric properties to ITO. The metal film has good conductivity and can replace part of the silver paste to transmit electrons. It has a good match with the work function of the silver paste, which can reduce the amount of indium used while reducing the silver consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of a heterojunction solar cell of the present invention;

[0019] Figure 2 It is a process flow chart of the present invention;

[0020] Description of reference numerals:

[0021] 1-N type silicon wafer;

[0022] 2-front intrinsic amorphous silicon layer;

[0023] 3-N-type doped amorphous silicon layer;

[0024] 4-back intrinsic amorphous silicon layer;

[0025] 5-P-type doped amorphous silicon layer;

[0026] 6-first transparent conductive layer;

[0027] 7- a second transparent conductive layer;

[0028] 8-metal conductive layer;

[0029] 9- a third transparent conductive layer;

[0030] 10- fourth transparent conductive layer;

[0031] 11- a fifth transparent conductive layer;

[0032] 12- back grid line;

[0033] 13-Front grid lines. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the invention clearer, the technical solution in the embodiments of the invention will be clearly and completely described below in combination with the embodiments of the invention. Obviously, the described embodiments are part of the embodiments of the invention, not all of the embodiments. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0035] Example

[0036] Step S1, selecting an N-type silicon wafer 1 as a silicon substrate, cleaning and texturing, obtaining a pyramid-shaped textured surface on both sides, wherein one side of the N-type silicon wafer 1 is referred to as the front side, and the other side is referred to as the back side;

[0037] Step S2, using PECVD to sequentially deposit a front intrinsic amorphous silicon layer 2 and an N-type doped amorphous silicon layer 3 on the front velvet surface; and sequentially deposit a back intrinsic amorphous silicon layer 4 and a P-type doped amorphous silicon layer 5 on the back velvet surface;

[0038] Step S3, depositing a first transparent conductive layer 6 on the P-type doped amorphous silicon layer 5. The first transparent conductive layer 6 is an ITO thin film, which is deposited by magnetron sputtering and has a thickness of 25-100 nm.

[0039] Step S4, depositing a second transparent conductive layer 7 on the first transparent conductive layer 6, wherein the second transparent conductive layer 7 is an AZO thin film, which is deposited by magnetron sputtering and has a thickness of 25-100 nm.

[0040] Step S5, depositing a metal conductive layer 8 on the second transparent conductive layer 7, wherein the metal conductive layer 8 is a highly conductive metal Cu thin film, which is deposited by magnetron sputtering and has a thickness of 200-500 nm.

[0041] Step S6, depositing a third transparent conductive layer 9 on the N-type doped amorphous silicon layer 3, wherein the third transparent conductive layer 9 is an ITO thin film, which is deposited by magnetron sputtering and has a thickness of 25-100 nm.

[0042] Step S7, depositing a fourth transparent conductive layer 10 on the third transparent conductive layer 9, wherein the fourth transparent conductive layer 10 is an AZO thin film, which is deposited by magnetron sputtering and has a thickness of 25-100 nm.

[0043] Step S8, depositing a fifth transparent conductive layer 11 on the fourth transparent conductive layer 10, wherein the fifth transparent conductive layer 11 is an ITO thin film, which is deposited by magnetron sputtering and has a thickness of 25-100 nm.

[0044] Step S9: manufacturing the front gate lines 13 and the back gate lines 12 on the fifth transparent conductive layer 11 and the metal conductive layer 8 respectively, and both the front gate lines and the back gate lines are realized by screen printing.

[0045] In heterojunction solar cells, the lateral transmission ability of photogenerated carriers on the amorphous silicon film layer is weak. The ITO film can be used to collect carriers and transmit them to the metal electrode. At the same time, the ITO transparent conductive film can also protect the PN junction and act as a reduction film to increase light absorption. Therefore, ITO films are deposited on both sides of the battery. The ITO film layer requires higher conductivity and transmittance, and a higher content of indium will increase the conductivity and transmittance of the film layer. Therefore, the amount of indium used in the ITO transparent conductive film is relatively high. The conductivity and transparency of AZO are slightly inferior to ITO, and AZO has poor acid and alkali resistance, poor atmospheric weather resistance, and is easily affected by water vapor. It is difficult for the battery to pass reliability verification and cannot completely replace ITO, but AZO has better thermal stability and is not easy to lose oxygen during heat treatment (relative to ITO).

[0046] Depositing a transparent conductive composite film layer on the front of an N-type heterojunction solar cell: I TO / AZO / I TO can not only reduce the amount of I TO used, as the cost of AZO target is only 25% of that of I TO target, but also ensure the light transmittance requirement on the front side, while also satisfying the atmospheric weather resistance of the transparent conductive film on the front side of the cell and good contact with semiconductor silicon.

[0047] A composite film layer is deposited on the back of an N-type heterojunction solar cell: ITO / AZO / Cu, wherein the metal Cu conductive film has better conductivity than ITO, and its good conductivity can replace the role of the fine grid silver paste on the back of the battery, reduce the amount of silver paste used, and reduce the total silver consumption of the battery by about 50%; the film layer structure uses ITO to ensure good contact with semiconductor silicon, AZO substitution reduces costs, and sputtering copper Cu can protect AZO from contacting the atmosphere; in addition, using AZO to contact Cu avoids the problem of large-scale diffusion of oxygen in ITO to the Cu film during the heat treatment of printed silver paste curing when ITO contacts Cu, and the oxygen diffusion process causes serious degradation of the optical properties of the ITO film and the Cu film.

[0048] The front and back TCO film layers of N-type heterojunction solar cells are both made of composite films to reduce the use of I TO, so that the total I TO consumption can be reduced by more than 50%; the purpose of reducing the consumption of In and Ag is achieved, achieving cost reduction without basically losing battery performance.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite TCO for a heterojunction solar cell, characterized in that: Select an N-type silicon wafer as a silicon substrate, clean and texture it to obtain a pyramid-shaped texture on both sides, with one side of the N-type silicon wafer being referred to as the front side and the other side being referred to as the back side; use PECVD to sequentially deposit a front intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer on the front texture surface; and sequentially deposit a back intrinsic amorphous silicon layer and a P-type doped amorphous silicon layer on the back texture surface; Depositing a first transparent conductive layer on the P-type doped amorphous silicon layer, depositing a second transparent conductive layer on the first transparent conductive layer, and depositing a metal conductive layer on the second transparent conductive layer; Depositing a third transparent conductive layer on the N-type doped amorphous silicon layer, depositing a fourth transparent conductive layer on the third transparent conductive layer, and depositing a fifth transparent conductive layer on the fourth transparent conductive layer; The back grid lines are printed on the metal conductive layer, and the front grid lines are printed on the fifth transparent conductive layer.

2. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The first transparent conductive layer is ITO, and the first transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

3. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The second transparent conductive layer is AZO, and the second transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

4. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The metal conductive layer is a highly conductive copper film, which is deposited by magnetron sputtering and has a thickness of 200-500 nm.

5. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The third transparent conductive layer is ITO, and the third transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

6. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The fourth transparent conductive layer is AZO, and is deposited by magnetron sputtering, with a thickness of 25-100 nm.

7. The method for preparing a composite TCO for a heterojunction solar cell according to claim 1, characterized in that: The fifth transparent conductive layer is ITO, and the fifth transparent conductive layer is deposited by magnetron sputtering, and has a thickness of 25-100 nm.

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