Preparation method of HJT photovoltaic cell electro-coppering electrode seed layer

Abstract

The invention discloses a preparation method of an HJT photovoltaic cell electro-coppering electrode seed layer, which adopts a CuNi target as a sputtering target material, introduces metallic nickel and controls the proportion of nickel, creatively adopts a novel CuNi seed layer film as a heterojunction cell electro-coppering seed layer, the CuNi seed layer film has good conductivity, and can be used for preparing an electro-coppering electrode seed layer. The CuNi seed layer film and the TCO film have good bonding strength, are easy to etch, do not have a corrosion expansion phenomenon, are matched with the etching rate of a copper film, have good acid resistance, have good matching degree with a copper electroplating solution, have good contact characteristics with the TCO film on the bottom layer in the electroplating solution, and are low in contact resistance; and the photoelectric conversion efficiency of the heterojunction solar cell can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of HJT photovoltaic cells, and in particular to a method for preparing a seed layer of an electroplated copper electrode of a HJT photovoltaic cell. Background Art

[0002] With the rapid development of the national economy, the continuous consumption of non-renewable energy, the increasing awareness of energy crisis, non-renewable energy such as coal, oil and natural gas are facing the risk of energy depletion, and the development of renewable energy such as wind energy, hydropower, solar energy, geothermal energy and tidal energy is imminent. Among them, photovoltaic solar energy has the advantages of being green, pollution-free and inexhaustible, and is considered one of the most promising green clean energy in the 21st century.

[0003] At present, the main way to utilize photovoltaic solar energy is photovoltaic power generation, the principle of which is the photovoltaic effect. When light is incident on the inside of a solar cell, under the excitation of photons, photogenerated carriers are generated inside the battery to form electrons and holes, and when the battery is connected to an external circuit, current is generated.

[0004] The mainstream solar cells on the market are PERC cells (passivated emitter and back contact cells, PERC cells for short). However, the photoelectric conversion efficiency of PERC cells is close to its highest theoretical efficiency of 24%. In order to further improve the conversion efficiency of cells, TOPcon cells (tunneling oxide passivated contact solar cells, TOPcon cells for short), HJT cells (heterojunction cells, HJT cells for short) and BC back contact cells (BC cells for short) using new technologies have emerged. Among them, HJT has become a recognized next-generation cell technology due to its simple process, high bifaciality, high photoelectric conversion efficiency and low attenuation.

[0005] However, the high manufacturing cost of HJT batteries has hindered their further market development. One of the main sources of their high cost is the use of screen-printed silver paste to prepare electrodes. The cost of silver paste is high, accounting for more than 50% of the non-silicon cost of HJT batteries. In order to reduce costs, people have proposed technologies such as MBB (multi-busbar technology, referred to as MBB), 0BB (busbar-free technology, referred to as 0BB), silver-coated copper, and electroplated copper. Among them, since electroplated copper technology can completely achieve desilvering and has a good match with HJT batteries, it is considered to be the ultimate technical route for desilvering. However, since traditional electroplating is non-selective, in order to prepare a selectively patterned electroplated copper electrode, it is necessary to first deposit a seed layer on the surface of the HJT battery TCO (transparent conductive oxide, referred to as TCO), and then obtain a patterned electroplated copper electrode after masking, exposure, development, electroplating and deseeding. The traditional seed layer is a copper seed layer film. However, since the copper seed layer is easily oxidized by water vapor in the air and has poor adhesion to TCO, corrosion expansion is likely to occur during etching, causing the copper electrode to easily fall off after electroplating, seriously affecting the photoelectric conversion efficiency of heterojunction solar cells. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a seed layer of an electroplated copper electrode for a HJT photovoltaic cell, using lower-cost copper to replace expensive silver, reducing the cost by more than 50%, and while significantly reducing the cost, unexpectedly improving the main performance of the cell and the photoelectric conversion efficiency.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing a seed layer of an electroplated copper electrode of a HJT photovoltaic cell, comprising the following steps:

[0008] A CuNi target is used as a sputtering target and a CuNi seed layer film is sputtered and deposited on the surface of the TCO blue film of the heterojunction solar cell by magnetron sputtering. The thickness of the CuNi seed layer film is 20-300nm. The TCO blue film uses the sputtered CuNi seed layer film as the seed layer of the electroplated copper electrode of the HJT cell photovoltaic cell.

[0009] The CuNi target has a CuNi mass ratio of Cu:Ni=(70-90):(10-30).

[0010] In a further technical solution, the density of the CuNi target is greater than or equal to 8.91 g / cm 3 The purity of the CuNi target is greater than or equal to 99.95%, the oxygen content of the CuNi target is less than 10 ppm, the target grain size of the CuNi target is small and uniform, the average grain size of the CuNi target is less than or equal to 55 μm and the maximum grain size is less than or equal to 80 μm.

[0011] In a further technical solution, the background vacuum of the magnetron sputtering is (0.5-5)×10 -3 Pa, the sputtering power density of the planar target is 0.5-6W / cm 2 , the sputtering power density of the corresponding rotating target is 1-12 kw / m, the sputtering pressure is 0.1-1 Pa, and the thickness of the CuNi seed layer film obtained by sputtering is 20-150 nm.

[0012] According to a further technical solution, the CuNi seed layer film has a rough microscopic surface structure, the arithmetic mean roughness Ra of the CuNi seed layer film is between 1.13nm and 6.64nm, and the root mean square roughness Rq is between 1.61nm and 7.51nm.

[0013] According to a further technical solution, the CuNi seed layer film has an arithmetic mean roughness Ra between 3-5 nm and a root mean square roughness Rq between 4-6 nm.

[0014] The advantages of the present invention compared with the prior art are:

[0015] The present invention adopts a CuNi target as a sputtering target material, introduces metallic nickel and controls the proportion of nickel, and innovatively adopts a novel CuNi seed layer film as a copper electroplating seed layer for a heterojunction battery. The CuNi seed layer film has good conductivity, and has good bonding strength with a TCO film. It is not only easy to etch, but also does not cause corrosion expansion. It also has good acid resistance, and has a good match with an electroplating solution. It has good contact characteristics with an underlying TCO film in the electroplating solution, and has low contact resistance.

[0016] The present invention adopts CuNi seed layer film to prepare electroplated copper electrode. Compared with traditional screen-printed electrodes, lower-cost copper is used to replace expensive silver, reducing the cost by more than 50%. While greatly reducing the cost, the main performance and photoelectric conversion efficiency of the battery are unexpectedly improved. The electroplated copper electrode HJT solar cell prepared by using CuNi seed layer film has significantly improved battery FF and greatly improved the photoelectric conversion efficiency by 0.2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a grain picture of the copper-nickel target material of Example 1 of the present invention.

[0018] Figure 2 This is the surface profile roughness curve of the CuNi film in Example 1 of the present invention.

[0019] Figure 3 It is a schematic diagram of the preparation process of the electroplated copper gate in Example 1 of the present invention.

[0020] Figure 4 This is a physical picture of the electroplated copper electrode HJT cell prepared using a CuNi seed layer in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] Example 1

[0022] A method for preparing a seed layer of an electroplated copper electrode for a HJT photovoltaic cell. Figures 1 to 4 As shown, the following steps are included:

[0023] A CuNi target is used as a sputtering target and a CuNi seed layer film is sputtered and deposited on the surface of a TCO blue film of a heterojunction solar cell by magnetron sputtering. The thickness of the CuNi seed layer film is 110±5nm. The TCO blue film uses the sputtered CuNi seed layer film as the seed layer of the electroplated copper electrode of the HJT photovoltaic cell.

[0024] The CuNi target used has a CuNi mass ratio of Cu:Ni=70:30.

[0025] The background vacuum of magnetron sputtering is 2×10 -3 Pa, sputtering power density is 1.5 W / cm 2 The sputtering pressure is 0.3 Pa, and the average thickness of the CuNi seed layer film obtained by sputtering is 110 nm.

[0026] The CuNi seed layer film has the advantages of good adhesion and low resistivity. The arithmetic mean roughness Ra of the CuNi seed layer film is between 1.13nm-6.64nm, and the root mean square roughness Rq is between 1.61nm-7.51nm. The high roughness is beneficial to improving the bonding strength between the CuNi seed layer film and the TCO film and the electroplated copper gate.

[0027] Under the AM1.5 standard light source, the HJT solar cell with electroplated copper electrode and the HJT solar cell with screen-printed silver paste electrode were tested, and the four key performance indicators of the cell's open circuit voltage Voc, short circuit current Isc, fill factor FF, and photoelectric conversion efficiency Eff were obtained. By comparison, the HJT cell with electroplated copper electrode has higher FF and Eff, and Voc and Isc are almost the same. The improvement of FF indirectly shows that the electroplated copper electrode using the CuNi seed layer film of the present invention has good conductivity and a smaller contact resistance with the TCO layer, which ultimately significantly improves the efficiency of the HJT cell with electroplated copper electrode by 0.2%, as shown in FIG.

[0028] As shown in Table 1.

[0029]

[0030] Table 1-Parameter test comparison table

[0031] The present invention forms a CuNi seed layer film by sputtering and depositing on a TCO blue film of a heterojunction solar cell using a CuNi target material through PVD magnetron sputtering. The CuNi seed layer film has good bonding strength with the TCO film and low contact resistance. The CuNi seed layer film is sputtered and deposited on the blue film and then sequentially subjected to mask processing, exposure processing, development processing, electroplating processing and seed layer removal processing to obtain a HJT solar cell with a patterned electroplated copper electrode.

[0032] According to tests, the seed layer electroplated copper electrode using the CuNi seed layer film of the present invention has an absolute improvement of more than 1% in FF and an absolute improvement of 0.2% in photoelectric conversion efficiency compared to a heterojunction cell using a traditional screen-printed silver paste electrode.

[0033] The CuNi target of the present invention is used as a sputtering target material. By introducing metallic nickel and controlling the proportion of nickel, a new CuNi seed layer film is innovatively used as a copper electroplating seed layer for a heterojunction battery. The CuNi seed layer film has good conductivity, and the CuNi seed layer film has good bonding strength with the TCO film. It is not only easy to etch, but also does not cause corrosion expansion. It also has good acid resistance and good matching with the electroplating solution. It has good contact characteristics with the underlying TCO film in the electroplating solution, and has low contact resistance.

[0034] The present invention adopts CuNi seed layer film to prepare electroplated copper electrode. Compared with traditional screen-printed electrodes, lower-cost copper is used to replace expensive silver, reducing the cost by more than 50%. While greatly reducing the cost, the main performance and photoelectric conversion efficiency of the battery are unexpectedly improved. The CuNi seed layer film is used to prepare electroplated copper electrode HJT solar cell, the battery FF is improved, and the photoelectric conversion efficiency is greatly improved by 0.2%.

[0035] Comparative Example 1

[0036] A high-purity Cu target with a purity of 99.99% was used for sputtering deposition on the surface of the TCO blue film. The copper film obtained by sputtering deposition was used as a seed layer. The thickness of the copper film was 150nm. The copper grid line underwent expansion and corrosion. After the copper electrode was electroplated on the seed layer, the copper electrode grid line fell off.

[0037] Comparative Example 2

[0038] A NiCr target is used for sputtering deposition on the surface of the TCO blue film, and the NiCr film obtained by sputtering deposition is used as a seed layer. The thickness of the NiCr film is 110 nm. The NiCr film is not compatible with the etching solution, and the etching rate is slow.

[0039] Comparative Example 3

[0040] A high-purity Mo target was used for sputtering deposition on the surface of the TCO blue film, and the Mo film obtained by sputtering deposition was used as a seed layer. The thickness of the Mo film was 150 nm. After the copper electrode was electroplated on the seed layer, the copper electrode grid line fell off.

[0041] Comparative Example 4

[0042] Ti target and Cu target are used for sputtering deposition on the surface of TCO blue film, and a composite film consisting of a 20nm thick Ti film and a 90nm thick Cu film obtained by sputtering deposition is used as a seed layer. After the copper electrode is electroplated on the seed layer, it does not match the etching solution and the etching rate is slow.

[0043] Comparative Example 5

[0044] MoNb target and Cu target are used for sputtering deposition on the surface of TCO blue film. A composite film consisting of a 20nm thick MoNb film and a 90nm thick Cu film obtained by sputtering deposition is used as a seed layer. After the copper electrode is electroplated on the seed layer, it does not match the etching solution and the etching rate is slow.

[0045] Comparative Example 6

[0046] NiCr target and Cu target are used for sputtering deposition on the surface of TCO blue film. A composite film consisting of a 20nm thick NiCr film and a 90nm thick Cu film obtained by sputtering deposition is used as a seed layer. After the copper electrode is electroplated on the seed layer, it does not match the etching solution and the etching rate is slow.

[0047] Comparative Example 7

[0048] Silver paste electrodes were prepared on TCO blue film by screen printing silver paste process, and HJT solar cells with silver paste electrodes were obtained as comparative examples.

Claims

1. A method for preparing a seed layer of an electroplated copper electrode for a HJT photovoltaic cell, characterized in that: The following steps are included: A CuNi target is used as a sputtering target and a CuNi seed layer film is sputtered and deposited on the surface of the TCO blue film of the heterojunction solar cell by magnetron sputtering. The thickness of the CuNi seed layer film is 20-300nm. The TCO blue film uses the sputtered CuNi seed layer film as the seed layer of the electroplated copper electrode of the HJT cell photovoltaic cell. The CuNi target has a CuNi mass ratio of Cu:Ni=(70-90):(10-30).

2. The method for preparing a HJT photovoltaic cell electroplating copper electrode seed layer according to claim 1, characterized in that: The density of the CuNi target is greater than or equal to 8.91 g / cm 3 The purity of the CuNi target is greater than or equal to 99.95%, the oxygen content of the CuNi target is less than 10 ppm, the target grain size of the CuNi target is small and uniform, the average grain size of the CuNi target is less than or equal to 55 μm and the maximum grain size is less than or equal to 80 μm.

3. The method for preparing a HJT photovoltaic cell electroplating copper electrode seed layer according to claim 1, characterized in that: The background vacuum degree of the magnetron sputtering is (0.5-5)×10 -3 Pa, the sputtering power density of the planar target is 0.5-6W / cm 2 , the sputtering power density of the corresponding rotating target is 1-12 kw / m, the sputtering pressure is 0.1-1 Pa, and the thickness of the CuNi seed layer film obtained by sputtering is 20-150 nm.

4. A method for preparing a HJT photovoltaic cell electroplating copper electrode seed layer according to any one of claims 1 to 3, characterized in that: The CuNi seed layer film has a rough microscopic surface structure. The arithmetic mean roughness Ra of the CuNi seed layer film is between 1.13nm and 6.64nm, and the root mean square roughness Rq is between 1.61nm and 7.51nm.

5. The method for preparing a HJT photovoltaic cell electroplating copper electrode seed layer according to claim 4, characterized in that: The CuNi seed layer film has an arithmetic mean roughness Ra between 3 and 5 nm, and a root mean square roughness Rq between 4 and 6 nm.

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