Solar cell and preparation method thereof

Abstract

According to the solar cell and the preparation method thereof disclosed by the invention, the anti-reflection performance of the cell is improved by introducing the anti-reflection layer, and parasitic absorption is reduced and short-circuit current is remarkably improved by combining the anti-reflection layer with the transparent conductive layer, so that the efficiency of the cell is improved. The transparent conducting layer is divided into a multi-layer structure, and the carrier concentration of the outer layer is controlled to be higher than that of the inner layer, so that relatively low electrode-transparent conducting layer contact resistivity can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a solar cell and its preparation method. Background Technology

[0002] Cost reduction and efficiency improvement have always been fundamental strategies in the solar energy industry. Among solar cells, heterojunction cells (HJTs) are a type of hybrid solar cell made using crystalline silicon substrates and amorphous silicon thin films. They have many advantages, such as simple fabrication process, low processing temperature, high open-circuit voltage, high photoelectric conversion efficiency, and low temperature coefficient, and are currently one of the most widely used high-efficiency crystalline silicon solar energy technologies.

[0003] In heterojunction solar cells (HJTs), many factors influence the short-circuit current, among which current loss due to parasitic absorption by the transparent conductive layer (TCO) is unavoidable. Furthermore, traditional transparent conductive layers often contain expensive indium materials, thus making the transparent conductive layer a significant obstacle to cost reduction in heterojunction solar cells.

[0004] Therefore, how to increase the short-circuit current of heterojunction cells (HJTs) to improve cell efficiency has become an urgent problem to be solved.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a solar cell and its preparation method, which can reduce parasitic absorption, increase short-circuit current, improve cell efficiency, and obtain a heterojunction cell with excellent optical and electrical properties.

[0007] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0008] A solar cell, comprising:

[0009] The photoelectric conversion unit includes a light-receiving surface and a backlight surface arranged opposite to each other;

[0010] A transparent conductive layer is located on the light-receiving surface and / or backlight surface of the photoelectric conversion unit. The transparent conductive layer includes an optical dominance layer and an electrode contact layer stacked along a direction away from the transparent conductive layer. The carrier concentration of the electrode contact layer is greater than the carrier concentration of the optical dominance layer.

[0011] An anti-reflection layer is located on the transparent conductive layer, and the anti-reflection layer has a window that penetrates into the transparent conductive layer;

[0012] The electrode is at least partially located within the window of the antireflective layer and is in contact with the transparent conductive layer.

[0013] In one or more embodiments of the present invention, the ratio of the thickness of the transparent conductive layer to the thickness of the antireflective layer is in the range of 0.8-1.2.

[0014] In one or more embodiments of the present invention, the thickness ratio of the transparent conductive layer to the antireflective layer is 1.

[0015] In one or more embodiments of the present invention, the thickness of the antireflection layer is 20nm-150nm.

[0016] In one or more embodiments of the present invention, the refractive index of the antireflection layer is 1.5-1.9.

[0017] In one or more embodiments of the present invention, the thickness of the transparent conductive layer is 20nm-150nm.

[0018] In one or more embodiments of the present invention, the antireflection layer is SiN. X SiO X SiNO X One or more composite membrane layers.

[0019] In one or more embodiments of the present invention, the thickness of the antireflection layer is 40nm-60nm.

[0020] In one or more embodiments of the present invention, the optical advantage layer and the electrode contact layer are made of the same material, the optical advantage layer is in electrical contact with the photoelectric conversion unit, and the electrode contact layer is in electrical contact with the antireflection layer and the electrode.

[0021] In one or more embodiments of the present invention, the thickness of the electrode contact layer is less than the thickness of the optical advantage layer.

[0022] In one or more embodiments of the present invention, the thickness of the electrode contact layer is 10nm-20nm, and the thickness of the optical advantage layer is 30nm-40nm.

[0023] In one or more embodiments of the present invention, the total thickness of the electrode contact layer and the optical advantage layer is 40nm-60nm.

[0024] In one or more embodiments of the present invention, the carrier concentration of the electrode contact layer is 2.0E20 / cm². 3 -6.5E20 / cm 3 The carrier concentration of the optical dominant layer is 1.5E20 / cm³. 3 -4.5E20 / cm3 .

[0025] In one or more embodiments of the present invention, the transparent conductive layer includes a first transparent conductive layer located on the light-receiving surface of the photoelectric conversion unit and a second transparent conductive layer located on the backlight surface of the photoelectric conversion unit;

[0026] The anti-reflection layer includes a first anti-reflection layer located on a first transparent conductive layer and a second anti-reflection layer located on a second transparent conductive layer;

[0027] The electrode includes a first electrode that is in electrical contact with a first transparent conductive layer and a second electrode that is in electrical contact with a second transparent conductive layer.

[0028] In one or more embodiments of the present invention, the solar cell is a heterojunction cell, and the photoelectric conversion unit includes:

[0029] A substrate, comprising a first surface and a second surface disposed opposite to each other, wherein the substrate is N-type doped or P-type doped;

[0030] The first intrinsic layer is located on the first surface of the substrate, and the first intrinsic layer is an intrinsic amorphous silicon layer and / or an intrinsic microcrystalline silicon layer.

[0031] The first doped layer is located on the first intrinsic layer. The first doped layer is an amorphous silicon layer and / or a microcrystalline silicon layer, and the doping type is the same as that of the substrate.

[0032] The second intrinsic layer is located on the second surface of the substrate, and the second intrinsic layer is an intrinsic amorphous silicon layer and / or an intrinsic microcrystalline silicon layer.

[0033] A second doped layer is located on the second intrinsic layer. The second doped layer is an amorphous silicon layer and / or a microcrystalline silicon layer, and the doping type is opposite to that of the substrate.

[0034] A method for preparing a solar cell, the method comprising the following steps:

[0035] Fabrication of photoelectric conversion units in solar cells;

[0036] A transparent conductive layer is formed on the light-receiving surface and / or backlight surface of the photoelectric conversion unit. The transparent conductive layer includes an optical dominance layer and an electrode contact layer stacked along a direction away from the transparent conductive layer. The carrier concentration of the electrode contact layer is greater than the carrier concentration of the optical dominance layer.

[0037] An anti-reflection layer is formed on the transparent conductive layer;

[0038] Laser technology is used to pattern the antireflective layer, forming a window that extends into the transparent conductive layer;

[0039] An electrode is fabricated within the window of the antireflection layer to contact the transparent conductive layer.

[0040] In one or more embodiments of the present invention, the preparation of the transparent conductive layer includes:

[0041] A transparent conductive layer is deposited on a photoelectric conversion unit by bombarding a target material using physical vapor deposition. Oxygen, hydrogen, and argon are introduced into the deposition chamber, and the temperature and gas flow rate within the deposition chamber are controlled to regulate the carrier concentration between the optical dominance layer and the electrode contact layer.

[0042] In one or more embodiments of the present invention, the preparation of the antireflection layer includes:

[0043] The temperature is controlled at 180℃-200℃, and an antireflection layer is deposited on the transparent conductive layer using a plasma-enhanced chemical vapor deposition process.

[0044] The antireflection layer is SiN. X SiO X SiNO X One or more composite membrane layers.

[0045] In one or more embodiments of the present invention, the electrode is prepared by screen printing or electroplating, and the curing temperature is 150°C to 300°C.

[0046] Compared with the prior art, the solar cell and its preparation method of the present invention introduce an antireflection layer and divide the transparent conductive layer into a multi-layer structure, controlling the carrier concentration of the outer layer to be higher than that of the inner layer (the outer layer is defined as the layer furthest from the photoelectric conversion unit), thereby obtaining a lower electrode-transparent conductive layer contact resistivity, reducing parasitic absorption, increasing short-circuit current, and improving cell efficiency.

[0047] The solar cell and its fabrication method of the present invention can obtain a heterojunction cell with excellent optical and electrical properties (high current, high conductivity, and low contact resistivity) by limiting the thickness ratio of the transparent conductive layer to the antireflection layer. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the structure of the solar cell in Embodiment 1 of the present invention;

[0050] Figure 2 This is a schematic diagram of the structure of the solar cell in Comparative Example 1 of the present invention;

[0051] Figure 3 This is a schematic diagram of the structure of the solar cell in Comparative Example 2 of the present invention. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0053] As mentioned in the background section, in heterojunction solar cells, current loss due to parasitic absorption of TCOs inevitably affects the short-circuit current. Furthermore, traditional TCO materials often contain high-cost indium, limiting cost-effective improvements to heterojunction solar cells.

[0054] Based on the fundamental strategy of cost reduction and efficiency improvement in the solar energy industry, this invention provides a solar cell and its fabrication method to improve the efficiency of heterojunction cells without significantly increasing costs, making improvements in two aspects. Firstly, an antireflection layer is introduced. The antireflection layer material is low-cost and has good antireflection properties. When used in conjunction with a transparent conductive layer (TCO), it reduces parasitic absorption and significantly increases short-circuit current, thereby improving cell efficiency. Secondly, by dividing the transparent conductive layer (TCO) into a multi-layer structure and controlling the carrier concentration of the outer layer to be higher than that of the inner layer (defined as the outer layer being furthest from the photoelectric conversion unit), a lower electrode-transparent conductive layer contact resistivity can be obtained. The properties of the TCO are adjustable, and the balance between optical and electrical performance is the criterion for judging the TCO quality factor. The multi-layer structure design of the TCO allows for optimal adjustment of both optical and electrical performance, ultimately resulting in a high-efficiency cell.

[0055] Example 1:

[0056] like Figure 1 As shown, the solar cell in this embodiment is a heterojunction cell, comprising:

[0057] The photoelectric conversion unit 10 includes a light-receiving surface and a backlight surface that are arranged opposite to each other.

[0058] A transparent conductive layer is located on the light-receiving surface and / or backlight surface of the photoelectric conversion unit 10. The transparent conductive layer includes an optical dominance layer and an electrode contact layer stacked along a direction away from the transparent conductive layer. The carrier concentration of the electrode contact layer is greater than that of the optical dominance layer.

[0059] An antireflective layer is located on the transparent conductive layer, and the antireflective layer has a window that extends through the transparent conductive layer.

[0060] The electrode is at least partially located within a window of the antireflective layer and is in contact with the transparent conductive layer.

[0061] In the above technical solution, by introducing an antireflection layer and dividing the transparent conductive layer into a multi-layer structure, the carrier concentration of the electrode contact layer (outer layer) is controlled to be higher than that of the optical advantage layer (inner layer), thereby obtaining a lower electrode-transparent conductive layer contact resistivity, reducing parasitic absorption, increasing short-circuit current, and improving battery efficiency.

[0062] In order to further obtain heterojunction solar cells with excellent optical and electrical properties (high current, high conductivity, and low contact resistivity), the thickness ratio of the transparent conductive layer to the antireflection layer is in the range of 0.8-1.2, preferably 1.

[0063] Preferably, the thickness of the antireflection layer is 20nm-150nm, more preferably 40nm-60nm. The refractive index of the antireflection layer is 1.5-1.9. The antireflection layer is SiN. X SiO X SiNO X One or more composite membrane layers.

[0064] Preferably, the thickness of the transparent conductive layer is 20nm-150nm, more preferably 40nm-60nm. The thickness of the electrode contact layer is less than the thickness of the optical dominance layer. The thickness of the electrode contact layer is 10nm-20nm, and the thickness of the optical dominance layer is 30nm-40nm.

[0065] Preferably, the optical dominance layer and the electrode contact layer are made of the same material. The optical dominance layer is in electrical contact with the photoelectric conversion unit 10, and the electrode contact layer is in electrical contact with the antireflection layer and the electrode. The carrier concentration of the electrode contact layer is 2.0E20 / cm². 3 -6.5E20 / cm 3 The carrier concentration of the optical dominant layer is 1.5E20 / cm³. 3 -4.5E20 / cm 3 .

[0066] refer to Figure 1As shown, the transparent conductive layer includes a first transparent conductive layer 20a located on the light-receiving surface of the photoelectric conversion unit 10 and a second transparent conductive layer 20b located on the backlight surface of the photoelectric conversion unit 10. The antireflection layer includes a first antireflection layer 30a located on the first electrode contact layer 22a and a second antireflection layer 30b located on the second electrode contact layer 22b. The thickness ratio of the first transparent conductive layer 20a to the thickness of the first antireflection layer 30a is between 0.8 and 1.2, preferably 1. The thickness ratio of the second transparent conductive layer 20b to the thickness of the second antireflection layer 30b is between 0.8 and 1.2, preferably 1.

[0067] The first transparent conductive layer 20a includes a first optical advantage layer 21a and a first electrode contact layer 22a stacked along a direction away from the first transparent conductive layer 20a. The first electrode contact layer 22a is stacked on the first optical advantage layer 21a. The carrier concentration of the first electrode contact layer 22a is greater than that of the first optical advantage layer 21a, and the thickness of the first electrode contact layer 22a is less than that of the first optical advantage layer 21a.

[0068] In this embodiment, the carrier concentration of the first optical dominant layer 21a is 1.5E20 / cm². 3 The thickness is 32 nm (glass sheet), and the carrier concentration of the first electrode contact layer 22a is 3.5 E20 / cm². 3 The thickness is 19nm.

[0069] The second transparent conductive layer 20b includes a second optical advantage layer 21b and a second electrode contact layer 22b stacked along a direction away from the second transparent conductive layer 20b. The second electrode contact layer 22b is stacked on top of the second optical advantage layer 21b. The carrier concentration of the second electrode contact layer 22b is greater than that of the second optical advantage layer 21b, and the thickness of the second electrode contact layer 22b is less than that of the second optical advantage layer 21b.

[0070] In this embodiment, the carrier concentration of the second optical dominant layer 21b is 2.3E20 / cm². 3 The thickness is 35 (glass sheet), and the carrier concentration of the second electrode contact layer 22b is 5.5E20 / cm². 3 The thickness is 12nm.

[0071] In this embodiment, the first antireflective layer 30a has a thickness of 50 nm and a refractive index of 1.8. The second antireflective layer 30b has a thickness of 50 nm and a refractive index of 1.9.

[0072] The electrodes include a first electrode 40a in electrical contact with the first electrode contact layer 22a and a second electrode 40b in electrical contact with the second electrode contact layer 22b. For example, the first antireflective layer 30a has a window exposing the first electrode contact layer 22a, and a portion of the first electrode 40a is formed within the window. Similarly, the second antireflective layer 30b has a window exposing the second electrode contact layer 22b, and a portion of the second electrode 40b is formed within the window.

[0073] The photoelectric conversion unit 10 is the main body of the heterojunction battery. The light-receiving surface is the front (or upper surface) of the main body, and the back-lighting surface is the back (or lower surface) of the main body.

[0074] Specifically, the photoelectric conversion unit 10 includes:

[0075] The substrate 11 includes a first surface (i.e., a front or upper surface) and a second surface (i.e., a back or lower surface) disposed opposite to each other, and the substrate is N-type doped or P-type doped;

[0076] The first intrinsic layer 121 is located on the first surface of the substrate 11. The first intrinsic layer 121 can be an intrinsic amorphous silicon layer or an intrinsic microcrystalline silicon layer.

[0077] The first doped layer 131 is located on the first intrinsic layer 121. The first doped layer 131 can be an amorphous silicon layer or a microcrystalline silicon layer, and the doping type is the same as the doping type of the substrate.

[0078] The second intrinsic layer 122 is located on the second surface of the substrate 11. The second intrinsic layer 122 can be an intrinsic amorphous silicon layer or an intrinsic microcrystalline silicon layer.

[0079] The second doped layer 132 is located on the second intrinsic layer 122. The second doped layer 132 can be an amorphous silicon layer or a microcrystalline silicon layer, and the doping type is opposite to that of the substrate.

[0080] Taking an N-type heterojunction solar cell as an example, the substrate 11 is an N-type substrate, the first doped layer 131 is N-type doped, and the second doped layer 132 is P-type doped.

[0081] The structure and photoelectric conversion principle of the photoelectric conversion unit in heterojunction solar cells are existing technologies and will not be elaborated here.

[0082] It should be understood that the electrode contact layer in this invention can be stacked on top of the optical advantage layer, or the electrode contact layer can be entirely or partially located inside the optical advantage layer.

[0083] Taking a heterojunction solar cell as an example, the method for fabricating a solar cell in this invention includes the following steps:

[0084] 1. Fabrication of photoelectric conversion units in solar cells.

[0085] 1.1 Provide silicon wafers.

[0086] The silicon wafer used in this invention is preferably an N-type monocrystalline silicon wafer with a resistivity of 0.5 Ω·cm-10 Ω·cm and a thickness of 90 μm-150 μm.

[0087] 1.2. Cleaning and flocking.

[0088] The oxide layer on the surface of the silicon wafer is removed by using a diluted 5% HF solution. Then, by using KOH, NaOH, or tetramethylammonium hydroxide (TMAH) with alcohol, a shallow pyramidal textured surface is formed on the surface through anisotropic etching of single-crystal silicon.

[0089] 1.3 Deposit an amorphous silicon layer.

[0090] First, SiH4 (silane) gas is introduced into the vacuum chamber, and a first intrinsic amorphous silicon layer is formed on the entire area of ​​the first surface of the N-type single crystal silicon wafer through plasma CVD process; then, SiH4 gas, H2 gas and PH3 (phosphine) gas are introduced into the vacuum chamber, and an N-type doped amorphous silicon layer is formed on the first intrinsic amorphous silicon layer through plasma CVD process.

[0091] Next, the wafer is flipped over, a new tray is placed, and SiH4 (silane) gas is introduced into the vacuum chamber. A second intrinsic amorphous silicon layer is formed on the entire area of ​​the second surface of the N-type single crystal silicon wafer using plasma CVD. Then, SiH4 gas, H2 gas, and B2H6 (diborane) gas are introduced into the vacuum chamber, and a P-type doped amorphous silicon layer is formed on the second intrinsic amorphous silicon layer using plasma CVD.

[0092] 2. A first transparent conductive layer is deposited on the light-receiving surface of the photoelectric conversion unit, and a second transparent conductive layer is deposited on the backlight surface of the photoelectric conversion unit.

[0093] On the amorphous silicon layers on the front and back sides, a physical vapor deposition (PVD) process is used for coating. The physical vapor deposition process can be reactive plasma deposition (RPD) or magnetron sputtering. The back side is edge-masked by a carrier disk design (or by a mask), and the specific masking area around the perimeter is -0.8mm.

[0094] During the fabrication of the transparent conductive layer, different transparent conductive layers are deposited sequentially on the substrate after the amorphous silicon layer is deposited, namely the optical advantage layer (inner transparent conductive layer) and the electrode contact layer (outer transparent conductive layer).

[0095] The specific method is as follows:

[0096] PVD mass production equipment has at least four non-contaminating coating target sites, each equipped with different target materials. The substrate is placed on a carrier plate and sequentially passes through different target sites for coating to obtain the desired film design. Process parameters are adjusted at different target sites to bring the carrier concentration of the transparent conductive layer within a preset range.

[0097] Physical vapor deposition (PVD) is a process that uses energy to bombard the phases in a target material while simultaneously introducing appropriate gases (oxygen O2, hydrogen H2, and argon Ar) to create a specific atmosphere. Different process conditions are selected for different transparent conductive layers.

[0098] 3. A first antireflection layer and a second antireflection layer are formed on the first transparent conductive layer and the second transparent conductive layer, respectively.

[0099] A low-temperature PECVD process is used, with the reaction temperature controlled at 180℃-200℃, to deposit an antireflection layer on a transparent conductive layer. The antireflection layer material can be SiN. X SiO X SiNO X One or more composite membrane layers.

[0100] 4. Pattern the first and second anti-reflection layers.

[0101] Using laser technology, windows penetrating to the first and second transparent conductive layers are formed on the first and second antireflective layers, respectively, exposing the first and second transparent conductive layers.

[0102] 5. Prepare a first electrode and a second electrode that are in contact with the first transparent conductive layer and the second transparent conductive layer, respectively.

[0103] A silver or copper electrode is printed on the transparent conductive layer on the front and back sides using screen printing or copper plating. Then, it is sintered and cured at a low temperature of 150℃-300℃ to form a good ohmic contact electrode.

[0104] The optical advantage layer and the electrode contact layer in this invention use the same TCO material. The two-layer structure can be carried out in the PVD deposition process. Only different process conditions need to be controlled, without adding new deposition steps.

[0105] It should be understood that when the electrode contact layer is stacked on top of the optical dominance layer, it can be achieved through normal deposition processes; when the electrode contact layer is entirely or partially located inside the optical dominance layer, it is necessary to design a physical mask or photolithographic mask to deposit the electrode contact layer only in the electrode formation area.

[0106] It should be understood that in the above Embodiment 1, a heterojunction battery is taken as an example for illustration. However, the present invention is not limited to heterojunction batteries and is also applicable to heterojunction back contact (HBC) batteries. In HBC batteries, the electrodes are formed on the backlight surface. Therefore, for HBC batteries, only the backlight surface needs to be provided with a transparent conductive layer and an antireflection layer. The specific processing technology is the same as that in the above embodiment and will not be elaborated here.

[0107] Comparative Example 1:

[0108] As Figure 2 shown, the solar cell in this Comparative Example 1 is a heterojunction battery, which includes:

[0109] A substrate 11, including a first surface and a second surface arranged oppositely, and the substrate is N-type doped;

[0110] A first intrinsic layer 121, located on the first surface of the substrate 11, and the first intrinsic layer 121 is an intrinsic amorphous silicon layer;

[0111] A first doped layer 131, located on the first intrinsic layer 121, and the first doped layer 131 is an N-type doped amorphous silicon layer;

[0112] A second intrinsic layer 122, located on the second surface of the substrate 11, and the second intrinsic layer 122 is an intrinsic amorphous silicon layer;

[0113] A second doped layer 132, located on the second intrinsic layer 122, and the second doped layer 132 is a P-type doped amorphous silicon layer;

[0114] A first transparent conductive layer 20a, with a carrier concentration of 3.0E20 / cm 3 , and a thickness of 90 nm (glass sheet);

[0115] A second transparent conductive layer 20b, with a carrier concentration of 3.5E20 / cm 3 , and a thickness of 110 nm (glass sheet);

[0116] A first electrode 40a, located on the first transparent conductive layer 20a and in electrical contact with it;

[0117] A second electrode 40b, located on the second transparent conductive layer 20b and in electrical contact with it.

[0118] Comparative Example 2:

[0119] As Figure 3 shown, the solar cell in this Comparative Example 2 is a heterojunction battery, which includes:

[0120] A substrate 11, including a first surface and a second surface arranged oppositely, and the substrate is N-type doped;

[0121] The first intrinsic layer 121 is located on the first surface of the substrate 11, and the first intrinsic layer 121 is an intrinsic amorphous silicon layer.

[0122] The first doped layer 131 is located on the first intrinsic layer 121, and the first doped layer 131 is an N-type doped amorphous silicon layer.

[0123] The second intrinsic layer 122 is located on the second surface of the substrate 11, and the second intrinsic layer 122 is an intrinsic amorphous silicon layer.

[0124] The second doped layer 132 is located on the second intrinsic layer 122, and the second doped layer 132 is a p-type doped amorphous silicon layer.

[0125] The first transparent conductive layer 20a has a carrier concentration of 2.7E20 / cm². 3 The thickness is 50nm (glass sheet);

[0126] The second transparent conductive layer 20b has a carrier concentration of 2.0E20 / cm². 3 The thickness is 50nm (glass sheet);

[0127] The first antireflective layer 30a is located on the first transparent conductive layer 20a, with a thickness of 50nm and a refractive index of 1.8.

[0128] The second antireflective layer 30b is located on the second transparent conductive layer 20b, with a thickness of 50nm and a refractive index of 1.9.

[0129] The first electrode 40a is in electrical contact with the first transparent conductive layer 20a;

[0130] The second electrode 40b is in electrical contact with the second transparent conductive layer 20b.

[0131] The performance parameters of the heterojunction cells in Comparative Examples 1 and 2 and Example 1, after testing, are shown in the table below:

[0132]

[0133] As can be seen, compared with Comparative Example 1 (a conventional battery without an antireflection layer), Example 1 shows an increase in overall Rs and a decrease in FF of 0.46% due to the presence of the antireflection layer, but with an optical gain of 0.55 mA / cm. 2 Therefore, the efficiency is improved by 0.21%. Compared with Comparative Example 2 (a monolayer TCO cell with an antireflection layer but without adjusting the carrier concentration), Example 1 shows a 0.05% reduction in FF, but an optical gain of 0.1 mA / cm². 2 Efficiency improved by 0.08%.

[0134] Compared with the prior art, the solar cell and its preparation method of the present invention introduce an antireflection layer and divide the transparent conductive layer into a multi-layer structure, controlling the carrier concentration of the outer layer to be higher than that of the inner layer (the outer layer is defined as the layer furthest from the photoelectric conversion unit), thereby obtaining a lower electrode-transparent conductive layer contact resistivity, reducing parasitic absorption, increasing short-circuit current, and improving cell efficiency.

[0135] The solar cell and its fabrication method of the present invention can obtain a heterojunction cell with excellent optical and electrical properties (high current, high conductivity, and low contact resistivity) by limiting the thickness ratio of the transparent conductive layer to the antireflection layer.

[0136] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0137] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A solar cell, characterized in that, include: The photoelectric conversion unit includes a light-receiving surface and a backlight surface arranged opposite to each other; A transparent conductive layer is located on the light-receiving surface and / or backlight surface of the photoelectric conversion unit. The transparent conductive layer includes an optical dominance layer and an electrode contact layer stacked along a direction away from the transparent conductive layer. The carrier concentration of the electrode contact layer is greater than the carrier concentration of the optical dominance layer. An anti-reflection layer is located on the transparent conductive layer, and the anti-reflection layer has a window that penetrates into the transparent conductive layer; The electrode is at least partially located within the window of the antireflective layer and is in contact with the transparent conductive layer.

2. The solar cell according to claim 1, characterized in that, The ratio of the thickness of the transparent conductive layer to the thickness of the antireflective layer is between 0.8 and 1.

2.

3. The solar cell according to claim 1, characterized in that, The thickness of the antireflective layer is 20nm-150nm; and / or, The thickness of the transparent conductive layer is 20nm-150nm; and / or, The refractive index of the antireflective layer is 1.5-1.

9.

4. The solar cell according to claim 1, characterized in that, The antireflection layer is SiN. X SiO X SiNO X One or more composite films; and / or, The thickness of the antireflective layer is 40nm-60nm.

5. The solar cell according to claim 1, characterized in that, The optical advantage layer and the electrode contact layer are made of the same material. The optical advantage layer is in electrical contact with the photoelectric conversion unit, and the electrode contact layer is in electrical contact with the antireflection layer and the electrode.

6. The solar cell according to claim 1, characterized in that, The thickness of the electrode contact layer is less than the thickness of the optical advantage layer; and / or, The thickness of the electrode contact layer is 10nm-20nm, and the thickness of the optical advantage layer is 30nm-40nm; and / or, The total thickness of the electrode contact layer and the optical advantage layer is 40nm-60nm.

7. The solar cell according to claim 1, characterized in that, The carrier concentration of the electrode contact layer is 2.0E20 / cm³. 3 -6.5E20 / cm 3 The carrier concentration of the optical dominant layer is 1.5E20 / cm³. 3 -4.5E20 / cm 3 .

8. The solar cell according to claim 1, characterized in that, The transparent conductive layer includes a first transparent conductive layer located on the light-receiving surface of the photoelectric conversion unit and a second transparent conductive layer located on the backlight surface of the photoelectric conversion unit; The anti-reflection layer includes a first anti-reflection layer located on a first transparent conductive layer and a second anti-reflection layer located on a second transparent conductive layer; The electrode includes a first electrode that is in electrical contact with a first transparent conductive layer and a second electrode that is in electrical contact with a second transparent conductive layer.

9. The solar cell according to claim 1, characterized in that, The solar cell is a heterojunction cell, and the photoelectric conversion unit includes: A substrate, comprising a first surface and a second surface disposed opposite to each other, wherein the substrate is N-type doped or P-type doped; The first intrinsic layer is located on the first surface of the substrate, and the first intrinsic layer is an intrinsic amorphous silicon layer and / or an intrinsic microcrystalline silicon layer. The first doped layer is located on the first intrinsic layer. The first doped layer is an amorphous silicon layer and / or a microcrystalline silicon layer, and the doping type is the same as that of the substrate. The second intrinsic layer is located on the second surface of the substrate, and the second intrinsic layer is an intrinsic amorphous silicon layer and / or an intrinsic microcrystalline silicon layer. A second doped layer is located on the second intrinsic layer. The second doped layer is an amorphous silicon layer and / or a microcrystalline silicon layer, and the doping type is opposite to that of the substrate.

10. A method for preparing a solar cell, characterized in that, The preparation method includes the following steps: Fabrication of photoelectric conversion units in solar cells; A transparent conductive layer is formed on the light-receiving surface and / or backlight surface of the photoelectric conversion unit. The transparent conductive layer includes an optical dominance layer and an electrode contact layer stacked along a direction away from the transparent conductive layer. The carrier concentration of the electrode contact layer is greater than the carrier concentration of the optical dominance layer. An anti-reflection layer is formed on the transparent conductive layer; Laser technology is used to pattern the antireflective layer, forming a window that extends into the transparent conductive layer; An electrode is fabricated within the window of the antireflection layer to contact the transparent conductive layer.

11. The preparation method according to claim 10, characterized in that, The preparation of the transparent conductive layer includes: A transparent conductive layer is deposited on a photoelectric conversion unit by bombarding a target material using physical vapor deposition. Oxygen, hydrogen, and argon are introduced into the deposition chamber, and the temperature and gas flow rate within the deposition chamber are controlled to regulate the carrier concentration between the optical dominance layer and the electrode contact layer.

12. The preparation method according to claim 10, characterized in that, The preparation of the antireflection layer includes: The temperature is controlled at 180℃-200℃, and an antireflection layer is deposited on the transparent conductive layer using a plasma-enhanced chemical vapor deposition process. The antireflection layer is SiN. X SiO X SiNO X One or more composite membrane layers.

13. The preparation method according to claim 10, characterized in that, The electrode is prepared by screen printing or electroplating, and the curing temperature is 150℃~300℃.

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