Composite film structure, solar cell and preparation method thereof

Abstract

The invention provides a composite film structure, a solar cell and a preparation method thereof, the composite film structure comprises at least one layer of composite structure film and an ITO film arranged on one side of the multi-layer composite structure film, the composite structure film comprises a first ITO film and an AZO film arranged on one side of the first ITO film, and the thickness of the first ITO film is different from that of the AZO film; the ITO film is arranged on one side of the AZO film of the outermost layer of composite structure film in the multiple layers of composite structure films. The preparation method has the beneficial effects that the AZO film is used for replacing part of the ITO film, so that the consumption of ITO is reduced, the cost is saved, the harm to a human body in the preparation process is reduced, the conductivity of the composite film structure is not reduced, the light transmittance of the TCO layer of the solar cell is increased, the light transmittance in a near-infrared region is particularly improved, the light absorption of the solar cell is increased, and meanwhile, the service life of the solar cell is prolonged. And the electrical property of the composite membrane structure is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a composite film structure, a solar cell and a preparation method thereof. Background Art

[0002] The HJT solar cell integrates the advantages of crystalline silicon and thin-film solar cells. It has attracted much attention in the industry of high-efficiency crystalline silicon cells due to its high efficiency, simple structure, low energy consumption and cost in the preparation process, low temperature coefficient, and large double-sided power generation. It has a double-sided symmetric structure, and the back surface can also collect scattered sunlight. The n-type bulk silicon layer is about 150 - 200 μm, and the bandgap width is about 1.12 eV. The n-type (n-a-Si:H) and p-type (p-a-Si:H) amorphous silicon doped layers are on both sides respectively, with a thickness of about 5 - 10 nm and a bandgap width of about 1.7 - 1.9 eV. Thus, a bandgap difference is generated, resulting in discontinuous energy bands at the interface. Then, an intrinsic hydrogenated amorphous silicon thin layer (i-a-Si:H) with a thickness of 5 - 10 nm is introduced. It can passivate the dangling bonds between amorphous silicon and crystalline silicon, reduce the contact barrier and leakage current, lower the interface state density, inhibit the tunneling current, and has a good buffering effect. The photo-generated carriers generated inside the cell are transmitted through the TCO layers on both sides and collected and led out through the grid electrodes printed on their surfaces, forming a simple structure of the heterojunction cell: front surface grid / light incident surface TCO / a-Si:H(n) / a-Si:H(i) / n-type crystalline silicon / a-Si:H(i) / a-Si:H(p) / backlight surface TCO / back surface grid.

[0003] In the HJT solar cell, due to the poor conductivity of the amorphous silicon layer (a-Si:H), in order to better collect and transport carriers, a TCO (Transparent Conductive Oxide) layer is added between the gate and a-Si:H as a connection to make up for the defect of insufficient lateral transport ability of the amorphous silicon layer and form a better Ohmic contact with the grid electrode. In addition to the light trapping effect of the textured surface structure, it also has an antireflection effect as a window layer.

[0004] ITO thin films are currently the most widely used TCO layers in heterojunction solar cells. They have a relatively high transmittance in the visible light region, but a relatively low transmittance in the near-infrared region. As the window layer of solar cells, they cannot maximize the utilization of sunlight. AZO has a high transmittance in both the visible light region and the near-infrared region, but its electrical properties are weaker compared to ITO. To obtain more efficient HJT cells, continuously enhancing the conductivity and light transmittance of the TCO layer is the key focus of research. Among existing TCO layers, ITO thin films have a low transmittance in the near-infrared region and cannot efficiently utilize sunlight. The ITO material contains the metal In, which is expensive and toxic. AZO thin films have good transmittance in the visible light region and the near-infrared region, but their electrical properties are average and their chemical resistance is also average, making them unsuitable as the TCO layer of solar cells. Summary of the Invention

[0005] In view of the above problems, the present invention provides a composite film structure, a solar cell, and a preparation method thereof to solve the above or other previous problems existing in the prior art.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a composite film structure, including at least one layer of composite structure film and an ITO film provided on one side of the multi-layer composite structure film, wherein,

[0007] The composite structure film includes a first ITO film and an AZO film provided on one side of the first ITO film, and the thickness of the first ITO film is different from the thickness of the AZO film;

[0008] The ITO film is provided on one side of the AZO film of the outermost layer of the multi-layer composite structure film.

[0009] Further, the thickness of the first ITO film is less than the thickness of the AZO film.

[0010] Further, the thickness of the ITO film is greater than the thickness of the AZO film.

[0011] Further, the thickness of the ITO film is 15 - 25 nm.

[0012] Further, the thickness of the first ITO film is 2 - 6 nm.

[0013] Further, the thickness of the AZO film is 4 - 8 nm.

[0014] A solar cell includes the composite film structure as described above, and the composite film structure is provided on both sides of a substrate.

[0015] A preparation method of a solar cell includes:

[0016] Setting up the ITO film target: setting the ITO film targets opposite to each other;

[0017] Set up the AZO film target: The AZO film targets are arranged opposite to each other, and the AZO film target is located on either side of the ITO film target;

[0018] Place the substrate between the oppositely arranged ITO film targets, and the AZO film target and the ITO film target on the same side of the substrate are in the same plane;

[0019] The substrate moves back and forth between the ITO film target and the AZO film target. Control the number of movement cycles of the substrate to deposit multiple layers of the first ITO film and AZO film.

[0020] Furthermore, the moving speed of the substrate is 5 - 30 mm / s, and the moving speed of the substrate between the ITO film targets is different from the moving speed of the substrate between the AZO film targets.

[0021] Furthermore, the AZO film target and the ITO film target form an ITO film and an AZO film on the substrate by magnetron sputtering.

[0022] Due to the above technical solution, the composite film structure has a multi-layer composite structure film. Each layer of the composite structure film includes a first ITO film and an AZO film, so that the composite film structure is not entirely composed of ITO films. Part of the ITO films are replaced by AZO films, reducing the usage amount of ITO, saving costs, reducing the harm to the human body during the preparation process, not reducing the electrical conductivity of the composite film structure, increasing the light transmittance of the TCO layer of the solar cell, especially increasing the transmittance in the near-infrared region, increasing the light absorption of the solar cell. At the same time, the electrical performance of the composite film structure is improved; the setting of the ITO film avoids the difficulty in coping with the next process of solar cell preparation due to the poor corrosion resistance of the AZO film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of the composite structure film of an embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of the composite film structure of an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of the substrate movement during the preparation of the composite film structure of an embodiment of the present invention.

[0026] In the figure:

[0027] 1. AZO film 2. First ITO film 3. ITO film DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0029] Figure 1 The structural schematic diagram of the composite film structure according to an embodiment of the present invention is shown. This embodiment relates to a composite film structure, a solar cell, and a preparation method thereof. The composite film structure has a multi-layer composite structure film, and the composite structure film includes a first ITO film and an AZO film, which keeps the conductivity of the composite film unchanged, improves the light transmittance of the composite film in the near-infrared region, and reduces the usage amount of In.

[0030] A composite film structure, as Figure 1 and 2 shown, is disposed on a substrate 6 to form the TCO layer of the solar cell. The composite film structure includes at least one composite structure film and an ITO film 3 disposed on one side of the multi-layer composite structure film. That is, the composite film structure includes a plurality of composite structure films sequentially disposed along the direction from the substrate 6 to the outside of the substrate 6, and on the outside of the plurality of composite structure films, an ITO film 3 is disposed to form the composite film structure. Among them, the composite structure film includes a first ITO film 2 and an AZO film 1 disposed on one side of the first ITO film 2. The setting of the composite structure film makes the first ITO film 2 and the AZO film 1 adjacent to each other, so that AZO can be incorporated into the first ITO film 2, reducing the carrier concentration in the first ITO film 2, and the transmittance of the AZO film 1 is good, so that the light transmittance of the entire composite film structure is increased, and the utilization rate of sunlight of the TCO layer of the solar cell is improved.

[0031] The conductivity of the composite film structure is related to the carrier concentration and mobility. Incorporating AZO into the first ITO film 2 reduces the carrier concentration of the first ITO film 2. At the same time, the mobility is related to the carrier concentration and the crystallization degree of the film. Therefore, the thickness of the first ITO film 2 is not the same as the thickness of the AZO film 1. The thicknesses of the first ITO film 2 and the AZO film 1 are selected according to actual needs, and no specific requirements are made here. In this embodiment, preferably, the thickness of the first ITO film 2 is less than the thickness of the AZO film 1, to avoid that when the thickness of the AZO film 1 is too low, the crystallization degree of the composite film structure is reduced, the grain boundary scattering becomes stronger, resulting in a reduction in mobility and a deterioration in electrical performance, and also to avoid that when the thickness of the AZO film 1 is too large, the entire composite film structure is mainly composed of the AZO film 1, and the carrier concentration is greatly reduced, resulting in a deterioration in electrical performance. Therefore, the thicknesses of the first ITO film 2 and the AZO film 1 need to be controlled according to actual needs.

[0032] The ITO film 3 is disposed on one side of the AZO film 1 of the outermost composite structure film in the multi-layer composite structure film. That is, the ITO film 3 is in contact with the AZO film 1 in the outermost composite structure film, to avoid that it is difficult for the solar cell to cope with the next process, such as electroplating copper, during the preparation process due to the poor corrosion resistance of the AZO film 1. The setting of the ITO film 3 enables the next process to proceed smoothly during the preparation process of the solar cell.

[0033] In this embodiment, the thickness of the ITO film 3 is different from that of the first ITO film 2, and the thickness of the ITO film 3 is different from that of the AZO film 1. Preferably, the thickness of the ITO film 3 is greater than that of the AZO film 1, and the thickness of the ITO film 3 is greater than that of the first ITO film 2.

[0034] In this embodiment, the thickness of the ITO film 3 is 15 - 25 nm, the thickness of the first ITO film 2 is 2 - 6 nm, and the thickness of the AZO film 1 is 4 - 8 nm.

[0035] A solar cell includes the composite film structure as described above. The composite film structure is disposed on the substrate 6 and is arranged on both side surfaces of the substrate 6.

[0036] A method for preparing a solar cell, as Figure 3 shown, includes:

[0037] Setting the ITO film target 4: The ITO film targets 4 are arranged oppositely. There are two ITO film targets 4, and the two ITO film targets 4 are arranged oppositely with a certain gap therebetween. This gap is selected according to the thickness of the substrate 6 and is greater than the thickness of the substrate 6.

[0038] Setting the AZO film target 5: The AZO film targets 5 are arranged oppositely. There are two AZO film targets 5, and the two AZO film targets 5 are arranged oppositely with a certain gap therebetween. This gap is selected according to the thickness of the substrate 6 and is greater than the thickness of the substrate 6. In order to form the composite film structure, this set of oppositely arranged AZO film targets 5 is located on either side of a set of oppositely arranged ITO film targets 4.

[0039] Placing the substrate 6 between the oppositely arranged ITO film targets 4. At the same time, the substrate 6 is also located between the oppositely arranged AZO film targets 5, and the AZO film target 5 and the ITO film target 4 on the same side of the substrate 6 are in the same plane, enabling the substrate 6 to move freely between the oppositely arranged ITO film targets 4 and between the oppositely arranged AZO film targets 5.

[0040] Control the movement of the substrate 6 so that the substrate 6 reciprocates between the ITO film target 4 and the AZO film target 5 to deposit the first ITO film 2, the ITO film 3, and the AZO film 1. During the movement of the substrate 6, when the substrate 6 moves from the ITO film target 4 to the AZO film target 5 and then returns, and moves from the AZO film target 5 to the ITO film target 4, it is one movement cycle of the substrate 6. Set this movement cycle as n. Each time the substrate 6 moves one movement cycle, a composite structure film is formed on both sides of the substrate 6. By controlling the value of the movement cycle n, the number of layers of the composite structure film on both sides of the substrate 6 can be obtained.

[0041] Therefore, the obtained composite film structure is (AB)n + ITO, where A is the first ITO film 2, B is the AZO film 1, and n is the number of movement cycles of the substrate 6. In this embodiment, n is greater than or equal to 1, and the value of n is selected according to actual needs. When 3 layers of composite structure films are required, then n is equal to 3.

[0042] The moving speed of the substrate 6 is 5 - 30 mm / s. The moving speed of the substrate 6 between the ITO film targets 4 is not the same as the moving speed of the substrate 6 between the AZO film targets 5, so as to control the thickness of the first ITO film 2 formed on the substrate 6 to be different from the thickness of the AZO film 1. In this embodiment, the moving speed of the substrate 6 between the ITO film targets 4 is less than the moving speed of the substrate 6 between the AZO film targets 5, so that the thickness of the first ITO film 2 is less than the thickness of the AZO film 1. According to the actual thickness of the first ITO film 2 and the AZO film 1, select the corresponding moving speed of the substrate 6. Since the total length of the equipment is the same, the faster the moving speed, the shorter the time, and the thinner the film thickness. Therefore, in this embodiment, preferably, when the substrate 6 moves between the ITO film targets 4 and between the AZO film targets 5, the time can be the same or different, and the moving speed and time of the substrate 6 are selected according to the thickness of the first ITO film 2 and the AZO film 1. There are no specific requirements here.

[0043] By means of magnetron sputtering, the AZO film target 5 and the ITO film target 4 form the first ITO film 2, the ITO film 3, and the AZO film 1 on the substrate 6. This magnetron detection method is prior art and will not be described in detail here. In this embodiment, the ITO film target 4 is indium tin oxide, and the AZO film target 5 is aluminum-doped zinc oxide.

[0044] The following is illustrated with a specific embodiment.

[0045] A composite film structure is disposed on both side surfaces of a substrate 6, including a three-layer composite structure film and an ITO film 3. The three-layer composite structure film and the ITO film 3 are sequentially arranged along the direction from the substrate 6 to the outside. In each layer of the composite structure film, it includes a first ITO film 2 and an AZO film 1 arranged adjacent to each other. The first ITO film 2 and the AZO film 1 are sequentially arranged along the direction from the substrate 6 to the outside. The thickness of the first ITO film 2 is 4 nm, the thickness of the AZO film 1 is 6 nm, and the thickness of the ITO film 3 is 20 nm.

[0046] An ITO film target 4 and an AZO film target 5 are provided. The number of ITO film targets 4 is two, which are oppositely arranged. The number of AZO film targets 5 is two, which are oppositely arranged. The substrate 6 is located between the ITO film targets 4. At the same time, during the movement of the substrate 6, it can move between the oppositely arranged ITO film targets 4 and between the oppositely arranged AZO film targets 5.

[0047] The moving speed of the substrate 6 is controlled. The moving speed between the ITO film targets 4 is 20 mm / s, and the moving speed between the AZO film targets 5 is 10 mm / s. The moving time of the substrate 6 between the ITO film targets 4 and between the AZO film targets 5 is the same. The number of movement cycles of the substrate 6 is 3 to form a three-layer composite structure film on both side surfaces of the substrate 6.

[0048] A solar cell includes the above composite film structure.

[0049] The conductivity of the TCO layer of the solar cell prepared by the above method is a sheet resistance of 75 Ω / sq, and the light transmittance is 86%.

[0050] Example Two

[0051] A composite film structure is disposed on both side surfaces of a substrate 6, including a three-layer composite structure film and an ITO film 3. The three-layer composite structure film and the ITO film 3 are sequentially arranged along the direction from the substrate 6 to the outside. In each layer of the composite structure film, it includes a first ITO film 2 and an AZO film 1 arranged adjacent to each other. The first ITO film 2 and the AZO film 1 are sequentially arranged along the direction from the substrate 6 to the outside. The thickness of the first ITO film 2 is 6 nm, the thickness of the AZO film 1 is 8 nm, and the thickness of the ITO film 3 is 25 nm.

[0052] An ITO film target 4 and an AZO film target 5 are provided. The number of ITO film targets 4 is two, which are oppositely arranged. The number of AZO film targets 5 is two, which are oppositely arranged. The substrate 6 is located between the ITO film targets 4. At the same time, during the movement of the substrate 6, it can move between the oppositely arranged ITO film targets 4 and between the oppositely arranged AZO film targets 5.

[0053] Control the moving speed of the substrate 6. The moving speed between the ITO film targets 4 is 25 mm / s, and the moving speed between the AZO film targets 5 is 15 mm / s. The moving time of the substrate 6 between the ITO film targets 4 and between the AZO film targets 5 is the same. The number of motion cycles of the substrate 6 is 3 to form a three-layer composite structure film on both sides of the substrate 6.

[0054] A solar cell includes the above composite film structure.

[0055] The conductivity of the TCO layer of the solar cell prepared by the above method is a sheet resistance of 80 Ω / sq, and the light transmittance is 83%.

[0056] Example 3

[0057] A composite film structure is provided on both sides of the substrate 6, including a four-layer composite structure film and a layer of ITO film 3. The three-layer composite structure film and a layer of ITO film 3 are arranged in sequence along the direction from the substrate 6 to the outside. In each layer of the composite structure film, it includes an adjacent first ITO film 2 and AZO film 1. The first ITO film 2 and AZO film 1 are arranged in sequence along the direction from the substrate 6 to the outside. The thickness of the first ITO film 2 is 4 nm, the thickness of the AZO film 1 is 6 nm, and the thickness of the ITO film 3 is 20 nm.

[0058] Set up ITO film targets 4 and AZO film targets 5. The number of ITO film targets 4 is two, which are arranged oppositely. The number of AZO film targets 5 is two, which are arranged oppositely. The substrate 6 is located between the ITO film targets 4. At the same time, during the movement of the substrate 6, it can move between the oppositely arranged ITO film targets 4 and between the oppositely arranged AZO film targets 5.

[0059] Control the moving speed of the substrate 6. The moving speed between the ITO film targets 4 is 15 mm / s, and the moving speed between the AZO film targets 5 is 8 mm / s. The moving time of the substrate 6 between the ITO film targets 4 and between the AZO film targets 5 is the same. The number of motion cycles of the substrate 6 is 4 to form a three-layer composite structure film on both sides of the substrate 6.

[0060] A solar cell includes the above composite film structure.

[0061] The conductivity of the TCO layer of the solar cell prepared by the above method is a sheet resistance of 78 Ω / sq, and the light transmittance is 84%.

[0062] Due to the adoption of the above technical solution, the composite film structure has a multi-layer composite structure film. Each layer of the composite structure film includes a first ITO film and an AZO film, so that the composite film structure is not entirely composed of ITO films. By replacing part of the ITO films with AZO films, the amount of ITO used is reduced, the cost is saved, the harm to the human body during the preparation process is reduced, the electrical conductivity of the composite film structure is not reduced, the light transmittance of the TCO layer of the solar cell is increased, especially the transmittance in the near-infrared region is improved, the light absorption of the solar cell is increased, and at the same time, the electrical performance of the composite film structure is enhanced. The setting of the ITO film avoids the difficulty in coping with the next process of solar cell preparation due to the poor corrosion resistance of the AZO film.

[0063] The above has described the embodiments of the present invention in detail, but the content described is only the preferred embodiments of the present invention and cannot be considered as defining the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A composite film structure, characterized in that: Comprising at least one layer of composite structure film and an ITO film disposed on one side of the multi-layer composite structure film, wherein, the composite structure film includes a first ITO film and an AZO film disposed on one side of the first ITO film, and the thickness of the first ITO film is different from the thickness of the AZO film; the ITO film is disposed on one side of the AZO film of the outermost layer of the multi-layer composite structure film.

2. The composite film structure according to claim 1, wherein: The thickness of the first ITO film is less than the thickness of the AZO film.

3. The composite film structure according to claim 1 or 2, characterized in that: The thickness of the ITO film is greater than the thickness of the AZO film.

4. The composite film structure according to claim 1 or 2, characterized in that: The thickness of the ITO film is 15 - 25 nm.

5. The composite film structure according to claim 4, wherein: The thickness of the first ITO film is 2 - 6 nm.

6. The composite film structure according to claim 5, wherein: The thickness of the AZO film is 4 - 8 nm.

7. A solar cell, characterized in that: Comprising the composite film structure according to any one of claims 1 - 6, wherein the composite film structure is disposed on both sides of a substrate.

8. A method for preparing a solar cell, characterized in that: Comprising: Setting the ITO film target: disposing the ITO film targets opposite to each other; Setting the AZO film target: disposing the AZO film targets opposite to each other, and the AZO film target is located on either side of the ITO film target; Placing the substrate between the oppositely disposed ITO film targets, and the AZO film target and the ITO film target on the same side of the substrate are in the same plane; The substrate reciprocates between the ITO film target and the AZO film target, and the number of movement cycles of the substrate is controlled to deposit multiple layers of the first ITO film and the AZO film.

9. The manufacturing method of the solar cell according to claim 8, wherein: The moving speed of the substrate is 5 - 30 mm / s, and the moving speed of the substrate between the ITO film targets is different from the moving speed of the substrate between the AZO film targets.

10. The method for preparing a solar cell according to claim 8 or 9, characterized in that: The AZO film target and the ITO film target form an ITO film and an AZO film on the substrate by means of magnetron sputtering.

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