Composite TCO thin film, heterojunction solar cell, and photovoltaic assembly

Abstract

The present disclosure relates to the technical field of solar cells, and discloses a composite TCO thin film, a heterojunction solar cell, and a photovoltaic assembly. The composite TCO thin film comprises a first TCO layer, a second TCO layer, and a mixed layer, stacked sequentially; the mixed layer comprises multiple conductive regions and multiple anti-reflection regions, the conductive regions and the anti-reflection regions both being in contact with the second TCO layer, and the conductive regions and the anti-reflection regions being alternatingly arranged.

Description

Composite TCO thin films, heterojunction solar cells and photovoltaic modules

[0001] Priority information

[0002] This application claims priority and benefits of patent application No. 202311288723.1 filed with the State Intellectual Property Office of China on September 28, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of solar cell technology, and in particular to a composite TCO film, a heterojunction solar cell and a photovoltaic module. Background Art

[0004] Silicon-based heterojunction solar cells (HJT) have simple process, low energy consumption, and high conversion efficiency. They have unique advantages in bifacial power generation and ultra-thin cells, and are an important direction for the future development of solar cells.

[0005] The typical HJT structure uses an N-type monocrystalline silicon wafer as the substrate. On one side of the monocrystalline silicon wafer, an intrinsic amorphous silicon layer and a doped N-type microcrystalline silicon layer are sequentially deposited. On the other side, an intrinsic amorphous silicon layer and a doped P-type microcrystalline silicon layer are sequentially deposited. Transparent conductive oxide (TCO) films are deposited on the surfaces of the N-type microcrystalline silicon layer and the P-type microcrystalline silicon layer, respectively. Finally, double-sided metal electrodes are formed on the top layer on both sides by screen printing. Because the emitter of the HJT cell has poor conductivity, current collection through metal grid lines alone is insufficient. Therefore, a TCO film that is both conductive and transparent is required to transport the charge. This requires the TCO film to have both good optical and electrical properties.

[0006] CN114914311A discloses a conductive layer consisting of, from the emitter upward, a first TCO layer, a second TCO layer, a third TCO layer, and a fourth TCO layer. The first TCO layer has a thickness of 2-6 nm and is used to collect amorphous silicon current; the second TCO layer has a thickness of 4-10 nm and is used for transition; the third TCO layer has a thickness of 80-100 nm and is used for light transmission; and the fourth TCO layer has a thickness of 5-10 nm and is used to match the metal electrode. This technical solution only considers improving the electrical matching between the traditional TCO film and the metal electrode and amorphous silicon, but ignores the fact that the outer film, with its high conductivity, is not conducive to visible light transmission, resulting in a low short-circuit current density of the battery, which is not conducive to improving battery performance.

[0007] Therefore, providing an improved TCO film that can better balance light transmittance and conductivity is of great significance for improving the performance of HJT.

[0008] Public content

[0009] The present disclosure addresses the problem that the TCO films of existing silicon-based heterojunction solar cells have difficulty in achieving both excellent light transmittance and electrical conductivity, which in turn leads to low short-circuit current density of silicon-based heterojunction solar cells. A composite TCO film, a heterojunction solar cell and a photovoltaic module are provided.

[0010] To achieve the above-mentioned object, the present disclosure provides a composite TCO film in a first aspect, wherein the composite TCO film comprises a first TCO layer (1), a second TCO layer (2) and a mixed layer (3) stacked in sequence;

[0011] The mixed layer (3) comprises a plurality of conductive regions (4) and a plurality of anti-reflection regions (5), and both the conductive regions (4) and the anti-reflection regions (5) are in contact with the second TCO layer (2), and the conductive regions (4) and the anti-reflection regions (5) are arranged alternately.

[0012] A second aspect of the present disclosure provides a heterojunction solar cell, comprising: an N-type single crystal silicon wafer substrate (101); a first intrinsic amorphous silicon layer (102), a P-type microcrystalline silicon layer (103), a first conductive layer (104), and a first metal electrode (105) arranged in sequence from near to far on the front side of the substrate; and a second intrinsic amorphous silicon layer (106), an N-type microcrystalline silicon layer (107), a second conductive layer (108), and a second metal electrode (109) arranged in sequence from near to far on the back side of the substrate;

[0013] The first conductive layer (104) is the composite TCO film described in the first aspect, and the first metal electrode (105) contacts and covers the conductive area (4) in the composite TCO film.

[0014] A third aspect of the present disclosure provides a photovoltaic module comprising the heterojunction solar cell described in the second aspect.

[0015] Through the above technical solution, the composite TCO film provided by the present disclosure has a multilayer film structure comprising a first TCO layer, a second TCO layer, and a mixed layer, wherein the mixed layer includes multiple conductive regions and multiple anti-reflection regions, and the conductive regions and the anti-reflection regions are both in contact with the second TCO layer, and the conductive regions and the anti-reflection regions are arranged alternately. Using this specific multilayer film structure, the TCO film can have a light transmittance of no less than 90% in the 400-1100nm band, while having a resistivity of only (2.3-3)×10 -4 Ω·cm, achieving both excellent light transmittance and electrical conductivity, thereby enabling the heterojunction solar cells using the composite TCO film to have higher short-circuit current density and fill factor, and higher conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a schematic diagram of the layer structure of the TCO film provided by the present disclosure.

[0017] FIG2 is a schematic diagram of the layer structure of a heterojunction solar cell provided by the present disclosure.

[0018] FIG3 is a schematic diagram of the front side (top view) of the heterojunction solar cell provided by the present disclosure.

[0019] Explanation of the accompanying drawings: 1-first TCO layer, 2-second TCO layer, 3-mixed layer, 4-conductive region, 5-anti-reflection region, 101-N-type single crystal silicon wafer substrate, 102-first intrinsic amorphous silicon layer, 103-P-type microcrystalline silicon layer, 104-first conductive layer, 105-first metal electrode, 106-second intrinsic amorphous silicon layer, 107-N-type microcrystalline silicon layer, 108-second conductive layer, 109-second metal electrode. DETAILED DESCRIPTION

[0020] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0021] In a first aspect, the present disclosure provides a composite TCO film, as shown in FIG1 , the composite TCO film comprises a first TCO layer 1 , a second TCO layer 2 , and a mixed layer 3 stacked in sequence;

[0022] The mixed layer 3 includes a plurality of conductive regions 4 and a plurality of anti-reflection regions 5 , and both the conductive regions 4 and the anti-reflection regions 5 are in contact with the second TCO layer 2 , and the conductive regions 4 and the anti-reflection regions 5 are alternately arranged.

[0023] In the present disclosure, a TCO film refers to a transparent conductive oxide (TCO) film, which exhibits high transmittance in the visible spectrum, a wide bandgap, and low resistivity, and is widely used in the field of solar cells. The inventors of the present disclosure have discovered that designing the TCO film as a composite structure comprising a first TCO layer, a second TCO layer, and a specific hybrid layer, wherein the hybrid layer is divided into different functional regions. Specifically, the functional regions include multiple conductive regions and multiple anti-reflection regions, and the conductive regions and the anti-reflection regions are both in contact with the second TCO layer. The conductive regions and the anti-reflection regions are arranged alternately. This allows the TCO film to have excellent optical and electrical properties, as demonstrated by high light transmittance in the 400-1100nm band and high electrical conductivity. This, in turn, improves the performance of heterojunction solar cells and increases the short-circuit current density of heterojunction solar cells.

[0024] In one embodiment, the conductive areas 4 and the anti-reflection areas 5 are arranged alternately, which means that in the mixed layer 3, the multiple conductive areas 4 do not contact each other, and each independently contacts the adjacent anti-reflection area 5 and the second TCO layer 2, and the end of each conductive area 4 facing away from the second TCO layer 2 is not completely covered by the anti-reflection area 5.

[0025] In the present disclosure, the number of the plurality of conductive regions 4 and anti-reflection regions 5 in the mixed layer 3 is relatively broad, as long as the number of the conductive regions 4 is consistent with the number of metal electrodes in the heterojunction solar cell, and the number of the anti-reflection regions 5 can achieve an alternating arrangement of the anti-reflection regions 5 and the conductive regions 4 (in the present disclosure, the number of conductive regions 4 and anti-reflection regions 5 shown in Figures 1, 2, and 3 is only used to illustrate the alternating arrangement of the two). In one embodiment, the number of the conductive regions 4 (denoted as n) is ≥ 8 (n is an integer). In one embodiment, the number n of the conductive regions 4 satisfies 8≤n≤20.

[0026] In one embodiment, when both ends of the mixed layer 3 (in the direction in which the conductive regions 4 and the anti-reflection regions 5 are alternately arranged) are conductive regions 4, the number of conductive regions 4 in the mixed layer 3 is n, and the number of anti-reflection regions 5 is n-1. In one embodiment, n ≥ 8 (n is an integer); in one embodiment, 8 ≤ n ≤ 20.

[0027] In one embodiment, when both ends of the mixed layer 3 (in the direction in which the conductive regions 4 and the anti-reflection regions 5 are alternately arranged) are the anti-reflection regions 5, the number of conductive regions 4 in the mixed layer 3 is n, and the number of anti-reflection regions 5 is n+1. In one embodiment, n ≥ 8 (n is an integer), and in one embodiment, 8 ≤ n ≤ 20.

[0028] In one embodiment, when the two ends of the mixed layer 3 (in the direction in which the conductive regions 4 and the anti-reflection regions 5 are alternately arranged) are the conductive regions 4 and the anti-reflection regions 5, respectively, the number of the conductive regions 4 and the anti-reflection regions 5 in the mixed layer 3 is n. In one embodiment, n ≥ 8 (n is an integer), and in one embodiment, 8 ≤ n ≤ 20.

[0029] In one embodiment, in the composite TCO film, the first TCO layer 1 has a high carrier concentration and excellent conductivity, primarily serving as a current collector. The second TCO layer 2 primarily serves as a conductor and transmits light, and also has an anti-reflection effect, capable of functioning as an anti-reflection film. The mixed layer 3 includes a conductive region 4 and an anti-reflection region 5. The conductive region 4 and the anti-reflection region 5 are in contact with each other and are not arranged in an upper and lower positional relationship, but rather both contact the second TCO layer 2. The anti-reflection region 5 primarily serves as an anti-reflection film. Since the anti-reflection region 5 contacts the second TCO layer 2, it can form a "double-layer anti-reflection film" with the second TCO layer 2, thereby significantly reducing light reflection in the visible light range and providing the composite TCO film with improved light transmittance. The conductive region 4 has a high carrier concentration and excellent conductivity. Since the conductive region 4 contacts the second TCO layer 2 and is not covered by the anti-reflection region 5, it can efficiently conduct current from the second TCO layer.

[0030] In one embodiment, in the composite TCO film, the material of the anti-reflection region 5 can be selected from MgF2, SiN x At least one of SiO2, Al2O3, TiO2 and ZnS can effectively reduce the reflectivity of incident light on the silicon wafer surface, which is beneficial to the absorption of incident light. In one embodiment, the material of the anti-reflection area 5 is selected from MgF2, SiN x and at least one of SiO2.

[0031] In one embodiment, in the composite TCO film, the materials of the first TCO layer 1 , the second TCO layer 2 and the conductive region 4 are independently selected from at least one of IWO, ITO, AZO, ICO and VTTO.

[0032] In the present disclosure, IWO refers to WO3-doped In2O3 material (the mass fraction of In2O3 is not less than 90%); ITO refers to SnO2-doped In2O3 material (the mass fraction of In2O3 is not less than 90%); AZO refers to Al2O3-doped ZnO material (the mass fraction of ZnO is not less than 98%); ICO refers to CeO2-doped InO3 material (the mass fraction of In2O3 is not less than 90%); VTTO refers to In2O3 material doped with multiple rare earth elements and metal oxides (the mass fraction of In2O3 is not less than 99%, purchased from Pioneer Thin Film Materials Co., Ltd.).

[0033] In one embodiment, in the multilayer structure of the composite TCO film, the first TCO layer 1, the second TCO layer 2, and the conductive region 4 can be made of the same material or different materials, which is not particularly limited in this disclosure. To improve film interface compatibility, in one embodiment, the first TCO layer 1, the second TCO layer 2, and the conductive region 4 are made of the same material.

[0034] In one embodiment of the present disclosure, the materials of the first TCO layer 1 , the second TCO layer 2 and the conductive region 4 are all ICO, which can bring higher carrier mobility and lower ICO / pa-Si:H interface contact resistance.

[0035] In the present disclosure, IWO, ITO, AZO, ICO, and VTTO are transparent conductive film materials known in the art and can be understood according to definitions known in the art.

[0036] In one embodiment, the composite TCO film can achieve a better balance between excellent light transmittance and electrical conductivity by regulating the contact area between the conductive region 4 and the second TCO layer 2, and the contact area between the anti-reflection region 5 and the second TCO layer 2. In one embodiment, the ratio of the contact area between the conductive region 4 and the second TCO layer 2 to the contact area between the anti-reflection region 5 and the second TCO layer 2 is (0.02-0.03):1.

[0037] In one embodiment, in the composite TCO film, the first TCO layer 1 has a thickness of 2-10 nm. In another embodiment, the first TCO layer 1 has a thickness of 4-6 nm. The thickness of the first TCO layer 1 falling within this range ensures both carrier collection in the doped layer and light transmittance.

[0038] In one embodiment, the thickness of the second TCO layer 2 in the composite TCO film is 70-110 nm. In another embodiment, the thickness of the second TCO layer 2 is 80-100 nm. A thickness of the second TCO layer 2 within this range can provide better optoelectronic performance and better form a "double-layer anti-reflection film" with the anti-reflection region of the hybrid layer.

[0039] In one embodiment, in the composite TCO film, the thickness of the mixed layer 3 is 80-150 nm. In another embodiment, the thickness of the mixed layer 3 is 100-120 nm. When the thickness of the mixed layer 3 falls within the above range, it can have better conductivity and thus better conduct carriers to the metal electrode.

[0040] In one embodiment, in the composite TCO film, the first TCO layer 1, the second TCO layer 2, and the mixed layer 3 meet the aforementioned thickness ranges. In one embodiment, the thickness ratio of the first TCO layer 1 to the second TCO layer 2 is 1:(7-40), which allows the composite TCO film to better balance excellent light transmittance and electrical conductivity.

[0041] In one embodiment, the composite TCO film has excellent light transmittance and high light transmittance. In a light transmittance test, the composite TCO film has a light transmittance of not less than 90% in the 400-1100 nm wavelength range.

[0042] In the present disclosure, light transmittance is measured according to the method specified in GB / T 30983-2014.

[0043] In one embodiment, the composite TCO film has excellent electrical conductivity. The resistivity of the composite TCO film is (2.3-3)×10 -4 Ω·cm.

[0044] In the present disclosure, the resistivity is measured according to the method specified in GB / T 4326-2006.

[0045] In one embodiment, the composite TCO film can be obtained by depositing a film layer by layer on a substrate using a target material. The target material used to deposit the first TCO layer 1, the second TCO layer 2 and the conductive area 4 can be selected from at least one of IWO, ITO, AZO, ICO and VTTO; the target material used to deposit the anti-reflection area 5 can be selected from MgF2, SiN x , SiO2, Al2O3, TiO2 and ZnS. The deposition coating can adopt conventional deposition coating processes and parameters in the art, including but not limited to magnetron sputtering, electron beam evaporation, reactive plasma deposition, etc.

[0046] In one embodiment, the preparation process of the composite TCO film includes: first, depositing the first TCO layer 1 on the substrate, the deposition conditions include: the gas is a mixture of high-purity argon and high-purity hydrogen, the high-purity hydrogen partial pressure accounts for 0.4-1%, the target power is 2-2.5kW, and the coating temperature is 170-190°C; then, the second TCO layer 2 is deposited on the surface of the first TCO layer 1, the deposition conditions include: the gas is a mixture of high-purity argon, high-purity hydrogen and high-purity oxygen, the high-purity hydrogen partial pressure accounts for 0.5-1.5%, the high-purity oxygen partial pressure accounts for 3-10%, the target power is 2-2.5kW, and the coating temperature is 170-190°C; then, a mask is set above the second TCO layer 2 (the opening of the mask corresponds to the guide The conductive region 4 is deposited on the surface of the second TCO layer 2 through a mask, and the deposition conditions include: the gas introduced is a mixture of high-purity argon and high-purity hydrogen, the partial pressure of high-purity hydrogen accounts for 1-1.5%, the target power is 2-2.5kW, and the coating temperature is 170-190°C; finally, the anti-reflection region 5 is deposited in the space other than the conductive region 4 on the surface of the second TCO layer 2, and the conductive region 4 and the anti-reflection region 5 together form the mixed layer 3, wherein, for depositing the anti-reflection region 5, when the material of the anti-reflection region 5 is MgF2, a polycrystalline granular raw material is used, and the thermal resistance method is used for evaporation, the resistance evaporation current is 85-90A, and the evaporation is smooth after pre-melting; when the material of the anti-reflection region 5 is SiN x When the anti-reflection region 5 is made of SiO2, Al2O3, TiO2 or ZnS, a tubular PECVD coating process is used, the gas introduced is a mixture of high-purity SiH4 and high-purity NH3, the volume ratio of NH3 / SiH4 is (3-4):1, the target power is 17-21kW, and the coating temperature is 200°C. When the anti-reflection region 5 is made of SiO2, Al2O3, TiO2 or ZnS, a radio frequency (13.56MHz) magnetron sputtering coating process is used, the gas introduced is high-purity argon (partial pressure 90-99.9%) and high-purity oxygen (partial pressure 0.1-10%), the target power is 1-5kW, and the coating temperature is 150-200°C. After the mixed layer 3 is deposited, the resulting composite film is annealed at 150-190°C to improve the overall crystallization of the film.

[0047] A second aspect of the present disclosure provides a heterojunction solar cell, as shown in FIG2 and FIG3 , the heterojunction solar cell comprising: an N-type single crystal silicon wafer substrate 101; a first intrinsic amorphous silicon layer 102, a P-type microcrystalline silicon layer 103, a first conductive layer 104, and a first metal electrode 105 disposed in sequence from near to far on the front surface of the substrate 101; and a second intrinsic amorphous silicon layer 106, an N-type microcrystalline silicon layer 107, a second conductive layer 108, and a second metal electrode 109 disposed in sequence from near to far on the back surface of the substrate 101;

[0048] The first conductive layer 104 is the composite TCO film described in the first aspect, and the first metal electrode 105 contacts and covers the conductive area 4 in the composite TCO film.

[0049] In the present disclosure, there is no particular limitation on the specifications and materials of the N-type single crystal silicon wafer substrate 101, the first intrinsic amorphous silicon layer 102, the P-type microcrystalline silicon layer 103, the first metal electrode 105, the second intrinsic amorphous silicon layer 106, the N-type microcrystalline silicon layer 107, the second conductive layer 108 and the second metal electrode 109 in the heterojunction solar cell, and conventional options in the field can be adopted.

[0050] In one embodiment, in the heterojunction solar cell, the upper surface of the conductive region 4 in the first conductive layer 104 completely overlaps with the lower surface of the first metal electrode 105 , which facilitates better longitudinal transmission of carriers to the metal electrode.

[0051] In the present disclosure, the P-type microcrystalline silicon layer refers to a silicon layer with P-type doping and a crystallization rate of more than 40%, and the N-type microcrystalline silicon layer refers to a silicon layer with N-type doping and a crystallization rate of more than 40%, which can be understood according to the definitions known in the art.

[0052] The heterojunction solar cell provided by the present disclosure comprises a first conductive layer using the specific composite TCO film disclosed herein. The composite TCO film can achieve both excellent light transmittance and electrical conductivity. Compared with heterojunction solar cell products using conventional TCO films as the first conductive layer, the heterojunction solar cell provided by the present disclosure has a higher short-circuit current density and fill factor, and a higher conversion efficiency.

[0053] A third aspect of the present disclosure provides a photovoltaic module comprising the heterojunction solar cell described in the second aspect.

[0054] The present disclosure will be described in detail below through examples. In the following examples and comparative examples,

[0055] Unless otherwise specified, all materials used are common commercially available products.

[0056] Example 1

[0057] Preparation of TCO thin film:

[0058] i) A clean, smooth glass sheet (75 mm × 25 mm, 1 mm thick) was placed in a coating machine and a thin film of ICO (1 wt% CeO2 + 99 wt% In2O3) was deposited on the glass sheet using magnetron sputtering (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 0.4%, a target power of 2.5 kW, and a coating temperature of 180°C) to form a first TCO layer;

[0059] ii) depositing an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film on the surface of the first TCO layer (using a mixture of high-purity argon, high-purity hydrogen, and high-purity oxygen, with the high-purity hydrogen partial pressure accounting for 1% and the high-purity oxygen partial pressure gradually increasing from 3% to 10%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a second TCO layer;

[0060] iii) a mask is disposed above the second TCO layer (the openings of the mask correspond to the deposition positions of the conductive regions), and an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film is deposited on the surface of the second TCO layer through the mask (the gas introduced is a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a conductive region; then, a MgF2 thin film is deposited on the surface of the second TCO layer excluding the conductive region (using a polycrystalline granular raw material, evaporated by a thermal resistance method, slowly adjusting the resistance evaporation current to 90 A, and steadily evaporating after pre-melting) to form an anti-reflection region. The conductive region and the anti-reflection region together form a mixed layer;

[0061] The obtained composite film was annealed at 190° C. for 30 min to obtain a composite TCO thin film (denoted as P1).

[0062] In P1, the thickness of the first TCO layer is 4nm, the thickness of the second TCO layer is 80nm, and the thickness of the mixed layer is 110nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:20; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.028:1.

[0063] Preparation of heterojunction solar cells:

[0064] 1) Texturing and cleaning of N-type single crystal silicon wafer (thickness 120nm);

[0065] 2) using PECVD to deposit a first intrinsic amorphous silicon layer (5 nm thick) on the front side of the N-type single crystal silicon wafer and a second intrinsic amorphous silicon layer (5 nm thick) on the back side, then depositing a P-type microcrystalline silicon layer (20 nm thick) on the surface of the first intrinsic amorphous silicon layer, and depositing an N-type microcrystalline silicon layer (25 nm thick) on the surface of the second intrinsic amorphous silicon layer;

[0066] 3) depositing the TCO film P1 on the surface of the P-type microcrystalline silicon layer of the silicon wafer (using the same process and parameters as described above for preparing the TCO film P1); and depositing a back TCO film (100 nm thick, made of ICO (i.e., 1 wt. % CeO2 + 99 wt. % In2O3)) on the surface of the N-type microcrystalline silicon layer of the silicon wafer.

[0067] 4) placing the coated silicon wafer obtained in step 3) in an annealing furnace for annealing at a temperature of 190° C. for 30 minutes;

[0068] 5) Depositing a layer of silver electrode on the conductive region of the mixed layer of the TCO film P1 and on the back TCO film by screen printing (wherein the front silver electrode completely overlaps with the upper surface of the conductive region of the mixed layer of P1) and curing the resulting heterojunction solar cell (denoted as B1).

[0069] Example 2

[0070] Preparation of TCO thin film:

[0071] i) A clean, smooth glass sheet (75 mm × 25 mm, 1 mm thick) was placed in a coating machine and an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film was deposited on the surface of the glass sheet by magnetron sputtering (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 0.4%, a target power of 2.5 kW, and a coating temperature of 180°C) to form a first TCO layer;

[0072] ii) depositing an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film on the surface of the first TCO layer (using a mixture of high-purity argon, high-purity hydrogen, and high-purity oxygen, with the high-purity hydrogen partial pressure accounting for 1% and the high-purity oxygen partial pressure gradually increasing from 3% to 10%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a second TCO layer;

[0073] iii) a mask is disposed above the second TCO layer (the openings of the mask correspond to the deposition positions of the conductive regions), and an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film is deposited on the surface of the second TCO layer through the mask (the gas introduced is a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a conductive region; then, a MgF2 thin film is deposited on the surface of the second TCO layer excluding the conductive region (using a polycrystalline granular raw material, evaporated by a thermal resistance method, slowly adjusting the resistance evaporation current to 90 A, and steadily evaporating after pre-melting) to form an anti-reflection region. The conductive region and the anti-reflection region together form a mixed layer;

[0074] The obtained composite film was annealed at 190° C. for 30 min to obtain a composite TCO thin film (denoted as P2).

[0075] In P2, the thickness of the first TCO layer is 6nm, the thickness of the second TCO layer is 105nm, and the thickness of the mixed layer is 150nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:17.5; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.02:1.

[0076] Preparation of heterojunction solar cells:

[0077] A heterojunction solar cell (denoted as B2) was obtained by following the method of Example 1, except that the TCO film P1 was replaced by the TCO film P2. Other conditions were the same as those of Example 1.

[0078] Example 3

[0079] Preparation of TCO thin film:

[0080] i) A clean, smooth glass sheet (75 mm × 25 mm, 1 mm thick) was placed in a coating machine and an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film was deposited on the surface of the glass sheet by magnetron sputtering (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 0.4%, a target power of 2.5 kW, and a coating temperature of 180°C) to form a first TCO layer;

[0081] ii) depositing an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film on the surface of the first TCO layer (using a mixture of high-purity argon, high-purity hydrogen, and high-purity oxygen, with the high-purity hydrogen partial pressure accounting for 1% and the high-purity oxygen partial pressure gradually increasing from 3% to 10%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a second TCO layer;

[0082] iii) a mask was placed above the second TCO layer (the openings in the mask corresponded to the deposition locations of the conductive regions), and an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film was deposited on the surface of the second TCO layer through the mask (the gas introduced was a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a conductive region; then, a MgF2 thin film was deposited on the surface of the second TCO layer excluding the conductive region (using a polycrystalline granular raw material, evaporated by a thermal resistance method, slowly adjusting the resistance evaporation current to 90 A, and then pre-melting and smoothly evaporating) to form an anti-reflection region. The conductive region and the anti-reflection region together formed a mixed layer;

[0083] The obtained composite film was annealed at 190° C. for 30 min to obtain a composite TCO thin film (denoted as P3).

[0084] In P3, the thickness of the first TCO layer is 2nm, the thickness of the second TCO layer is 75nm, and the thickness of the mixed layer is 100nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:37.5; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.03:1.

[0085] Preparation of heterojunction solar cells:

[0086] The method of Example 1 is followed, except that the TCO film P1 is replaced by the above-mentioned TCO film P3. Other conditions are the same as those of Example 1, to obtain a heterojunction solar cell (denoted as B3).

[0087] Example 4

[0088] Preparation of TCO thin film:

[0089] i) A clean, smooth glass sheet (75 mm × 25 mm, 1 mm thick) was placed in a coating machine and an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film was deposited on the surface of the glass sheet by magnetron sputtering (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 0.4%, a target power of 2.5 kW, and a coating temperature of 180°C) to form a first TCO layer;

[0090] ii) depositing an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film on the surface of the first TCO layer (using a mixture of high-purity argon, high-purity hydrogen, and high-purity oxygen, with the high-purity hydrogen partial pressure accounting for 1% and the high-purity oxygen partial pressure gradually increasing from 3% to 10%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a second TCO layer;

[0091] iii) a mask was placed above the second TCO layer (the openings in the mask corresponded to the deposition locations of the conductive regions), and an ITO (3 wt% SnO2 + 97 wt% In2O3) thin film was deposited on the surface of the second TCO layer through the mask (the gas introduced was a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a conductive region; then, a MgF2 thin film was deposited on the surface of the second TCO layer excluding the conductive region (using a polycrystalline granular raw material, evaporated by a thermal resistance method, slowly adjusting the resistance evaporation current to 90 A, and then pre-melting and smoothly evaporating) to form an anti-reflection region. The conductive region and the anti-reflection region together formed a mixed layer;

[0092] The obtained composite film was annealed at 190° C. for 30 min to obtain a composite TCO thin film (denoted as P4).

[0093] In P4, the thickness of the first TCO layer is 10nm, the thickness of the second TCO layer is 110nm, and the thickness of the mixed layer is 130nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:11; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.022:1.

[0094] Preparation of heterojunction solar cells:

[0095] The method of Example 1 is followed, except that the TCO film P1 is replaced by the above-mentioned TCO film P4. Other conditions are the same as those of Example 1, to obtain a heterojunction solar cell (denoted as B4).

[0096] Example 5

[0097] Preparation of TCO thin film:

[0098] According to the method of Example 4, except that the deposition thickness of the mixed layer is changed, other conditions are the same as Example 4, and a TCO thin film (denoted as P5) is obtained;

[0099] In P5, the thickness of the first TCO layer is 10 nm, the thickness of the second TCO layer is 110 nm, and the thickness of the mixed layer is 110 nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:11; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.022:1.

[0100] Preparation of heterojunction solar cells:

[0101] The method of Example 4 is followed, except that the TCO film P4 is replaced by the above-mentioned TCO film P5. Other conditions are the same as those of Example 4, to obtain a heterojunction solar cell (denoted as B5).

[0102] Example 6

[0103] Preparation of TCO thin film:

[0104] The method of Example 4 is as follows, except that the material of the anti-reflection area is replaced with SiN x (A tubular PECVD coating process was used, the inlet gas was a mixture of high-purity SiH4 and high-purity NH3, the NH3 / SiH4 ratio was 3.34, the target power was 18 kW, and the coating temperature was 200°C.) Other conditions were the same as those in Example 4, and a TCO film (denoted as P6) was obtained.

[0105] In P6, the thickness of the first TCO layer is 10nm, the thickness of the second TCO layer is 110nm, and the thickness of the mixed layer is 130nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:11; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.022:1.

[0106] Preparation of heterojunction solar cells:

[0107] The method of Example 4 is followed, except that the TCO film P4 is replaced by the above-mentioned TCO film P6. Other conditions are the same as those of Example 4, to obtain a heterojunction solar cell (denoted as B6).

[0108] Example 7

[0109] Preparation of TCO thin film:

[0110] A TCO film (denoted as P7) was obtained by following the method of Example 4, except that the contact area between the conductive region and the second TCO layer and the contact area between the anti-reflection region and the second TCO layer were changed. Other conditions were the same as those of Example 4.

[0111] In P7, the thickness of the first TCO layer is 10nm, the thickness of the second TCO layer is 110nm, and the thickness of the mixed layer is 130nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:11; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.03:1.

[0112] Preparation of heterojunction solar cells:

[0113] The method of Example 4 is followed, except that the TCO film P4 is replaced by the above-mentioned TCO film P7. Other conditions are the same as those of Example 4, to obtain a heterojunction solar cell (denoted as B7).

[0114] Example 8

[0115] Preparation of TCO thin film:

[0116] A TCO thin film (denoted as P8) was obtained by following the method of Example 4, except that the total deposition thickness of the first TCO layer, the second TCO layer, and the mixed layer was kept the same as that of Example 4, and the deposition thickness of each of the first TCO layer, the second TCO layer, and the mixed layer was changed. Other conditions were the same as those of Example 4, and a TCO thin film was obtained.

[0117] In P8, the thickness of the first TCO layer is 2nm, the thickness of the second TCO layer is 100nm, and the thickness of the mixed layer is 148nm; the thickness ratio of the first TCO layer to the second TCO layer is 1:50; the ratio of the contact area between the conductive area and the second TCO layer to the contact area between the anti-reflection area and the second TCO layer is 0.022:1.

[0118] Preparation of heterojunction solar cells:

[0119] The method of Example 4 is followed, except that the TCO film P4 is replaced by the above-mentioned TCO film P8. Other conditions are the same as those of Example 4, to obtain a heterojunction solar cell (denoted as B8).

[0120] Comparative Example 1

[0121] Preparation of TCO thin film:

[0122] The method of Example 1 was followed, except that in step iii), an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film was deposited on the surface of the second TCO layer (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a third TCO film. Other operations and conditions were the same as in Example 1, yielding a TCO thin film (denoted as DP1).

[0123] In DP1, the thickness of the first TCO layer is 4 nm, the thickness of the second TCO layer is 80 nm, and the thickness of the third TCO layer is 110 nm.

[0124] Preparation of heterojunction solar cells:

[0125] The method of Example 1 is followed, except that the TCO film P1 is replaced by the above-mentioned TCO film DP1. Other conditions are the same as those of Example 1, to obtain a heterojunction solar cell (denoted as DB1).

[0126] Comparative Example 2

[0127] Preparation of TCO thin film:

[0128] i) A clean, smooth glass sheet (75 mm × 25 mm, 1 mm thick) was placed in a coating machine and a thin film of ICO (1 wt% CeO2 + 99 wt% In2O3) was deposited on the glass sheet using magnetron sputtering (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 0.4%, a target power of 2.5 kW, and a coating temperature of 180°C) to form a first TCO layer;

[0129] ii) depositing an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film on the surface of the first TCO layer (using a mixture of high-purity argon, high-purity hydrogen, and high-purity oxygen, with the high-purity hydrogen partial pressure accounting for 1% and the high-purity oxygen partial pressure gradually increasing from 3% to 10%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a second TCO layer;

[0130] iii) depositing an ICO (1 wt% CeO2 + 99 wt% In2O3) thin film on the surface of the second TCO layer (using a mixture of high-purity argon and high-purity hydrogen, with a high-purity hydrogen partial pressure of 1%, a target power of 2.5 kW, and a deposition temperature of 180°C) to form a third TCO film;

[0131] iv) depositing a MgF2 thin film on the surface of the third TCO layer (using polycrystalline granular raw material, evaporation by thermal resistance method, slowly adjusting the resistance evaporation current to 90A, and evaporating steadily after pre-melting) to form a MgF2 layer;

[0132] The obtained composite film was annealed at 190° C. for 30 min to obtain a composite TCO thin film (denoted as DP2).

[0133] In DP2, the thickness of the first TCO layer is 4 nm, the thickness of the second TCO layer is 80 nm, the thickness of the third TCO layer is 10 nm, and the thickness of the MgF2 layer is 100 nm.

[0134] Preparation of heterojunction solar cells:

[0135] The method of Example 1 is followed, except that the TCO film P1 is replaced by the TCO film DP2. Other conditions are the same as those of Example 1, to obtain a heterojunction solar cell (denoted as DB2).

[0136] Test Case

[0137] The above TCO films P1-P8 and DP1-DP2 were subjected to light transmittance test and resistivity test, respectively. The results are shown in Table 1.

[0138] Light transmittance test: According to the method specified in GB / T 30983-2014, the average light transmittance of the TCO film was measured at 25°C using a UV-visible spectrophotometer with blank glass as the control.

[0139] Conductivity test: According to the method specified in GB / T 4326-2006, the thin film was deposited on a glass slide at 25°C and the resistivity of the TCO film was measured using a Hall effect tester.

[0140] The above-mentioned heterojunction solar cells B1-B8 and DB1-DB2 were subjected to IV tests respectively. A solar simulator was used to simulate sunlight irradiating onto the cells. The IV characteristics of the cells were tested using a digital source meter. The short-circuit current density and fill factor of the cells were calculated. The results are shown in Table 2.

[0141] Table 1

[0142] Table 2

[0143] As can be seen from Tables 1 and 2, the composite TCO films P1-P8 provided by the present disclosure adopt a composite structure comprising a first TCO layer, a second TCO layer, and a mixed layer, and the mixed layer is divided into a conductive area and an anti-reflection area that are in contact with each other. Compared with traditional TCO films, the composite TCO films P1-P8 can better balance light transmittance and conductivity, and can achieve a light transmittance of not less than 90% in the 400-1100nm band of the TCO films, and at the same time have a (2.3-3)×10 -4 The low resistivity of Ω·cm enables heterojunction solar cells to achieve higher short-circuit current density and fill factor, resulting in excellent electrical and optical performance. In particular, the TCO films provided in Comparative Examples 1 and 2 lack the structure of the composite TCO films disclosed herein, and their optoelectronic performance is inferior to that of P1-P8.

[0144] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A composite TCO film, wherein: The composite TCO film comprises a first TCO layer (1), a second TCO layer (2) and a mixed layer (3) which are stacked in sequence; The mixed layer (3) comprises a plurality of conductive regions (4) and a plurality of anti-reflection regions (5), and both the conductive regions (4) and the anti-reflection regions (5) are in contact with the second TCO layer (2), and the conductive regions (4) and the anti-reflection regions (5) are arranged alternately.

2. The composite TCO film according to claim 1, wherein: The material of the anti-reflection zone (5) is selected from MgF2, SiN x , SiO2, Al2O3, TiO2 and ZnS.

3. The composite TCO film according to claim 1 or 2, wherein: The materials of the first TCO layer (1), the second TCO layer (2) and the conductive area (4) are independently selected from at least one of IWO, ITO, AZO, ICO and VTTO.

4. The composite TCO film according to any one of claims 1 to 3, wherein: The ratio of the contact area between the conductive region (4) and the second TCO layer (2) to the contact area between the anti-reflection region (5) and the second TCO layer (2) is (0.02-0.03):

1.

5. The composite TCO film according to any one of claims 1 to 4, wherein: The thickness of the first TCO layer (1) is 2-10 nm; Alternatively, the thickness of the first TCO layer (1) is 4-6 nm.

6. The composite TCO film according to any one of claims 1 to 5, wherein: The thickness of the second TCO layer (2) is 70-110 nm; Alternatively, the thickness of the second TCO layer (2) is 80-100 nm.

7. The composite TCO film according to any one of claims 1 to 6, wherein: The thickness of the mixed layer (3) is 80-150 nm; Alternatively, the thickness of the mixed layer (3) is 100-120 nm.

8. The composite TCO film according to any one of claims 1 to 7, wherein: The thickness ratio of the first TCO layer (1) to the second TCO layer (2) is 1:(7-40).

9. The composite TCO film according to any one of claims 1 to 8, wherein: In a light transmittance test, the composite TCO film has a light transmittance greater than 90% in the 400-1100 nm wavelength range.

10. The composite TCO film according to any one of claims 1 to 9, wherein: The resistivity of the composite TCO film is (2.3-3)×10 -4 Ω·cm.

11. A heterojunction solar cell, wherein: The heterojunction solar cell comprises: an N-type single crystal silicon wafer substrate (101), a first intrinsic amorphous silicon layer (102), a P-type microcrystalline silicon layer (103), a first conductive layer (104) and a first metal electrode (105) arranged in sequence from near to far on the front side of the substrate, and a second intrinsic amorphous silicon layer (106), an N-type microcrystalline silicon layer (107), a second conductive layer (108) and a second metal electrode (109) arranged in sequence from near to far on the back side of the substrate; The first conductive layer (104) is the composite TCO film according to any one of claims 1 to 10, and the first metal electrode (105) contacts and covers the conductive area (4) in the composite TCO film.

12. A photovoltaic module, wherein: Including the heterojunction solar cell as described in claim 11.

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