A cadmium telluride thin film solar cell based on a doped tin carbide back contact layer and a preparation method thereof

Abstract

The application discloses a cadmium telluride thin film solar cell based on a doped tin carbide back contact layer and a preparation method thereof. The cadmium telluride thin film solar cell comprises a substrate layer, a transparent conductive oxide thin film layer, a high-resistance buffer layer, a window layer, a cadmium telluride absorption layer, a back contact layer and a back electrode layer arranged in sequence. The back contact layer is deposited by tin carbide doped with a beta element. The beta element is one or more of boron, aluminum, gallium, indium and thallium. The doping amount of the beta element is 0.1-1.0% in mass ratio. The cadmium telluride thin film solar cell has the advantages that the back contact layer doped with tin carbide can reduce the recombination of holes at the interface between CdTe and a metal electrode, optimizes the collection and transmission efficiency of the holes, and improves the efficiency of the cadmium telluride thin film solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell material technology, and particularly relates to a cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer and its preparation method. Background Technology

[0002] Cadmium telluride thin-film solar cells, as a highly efficient photovoltaic technology, have attracted widespread attention due to their high conversion efficiency, low manufacturing cost, and good temperature coefficient. The core of this cell lies in its unique five-layer structure, including a glass substrate, a transparent conductive oxide thin film layer (TCO layer), a CdS window layer, a CdTe absorber layer, and, crucially, a back contact layer and a back electrode layer.

[0003] The back contact layer plays a crucial role in the battery. It not only needs to lower the contact barrier between CdTe and the metal electrode, but also needs to draw current and ensure a good ohmic contact between the metal electrode and CdTe. Significant progress has been made in back contact layer technology; for example, the phase composition of the reaction between Cu and Te can be optimized by changing the Cu content in the back contact layer. 1.4 Te-dominated back contact buffer layers can effectively reduce the "flipping" phenomenon in the battery IV curve and lower the back contact barrier, but some challenges still exist, such as the easy diffusion of copper ions at high temperatures leading to battery performance degradation. Summary of the Invention

[0004] The problem solved by this invention is to provide a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer and its preparation method, so as to optimize the hole collection and transport efficiency and improve the efficiency of the cell.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer includes a substrate layer, a transparent conductive oxide thin film layer, a high-resistivity buffer layer, a window layer, a cadmium telluride absorber layer, a back contact layer, and a back electrode layer arranged sequentially.

[0007] The back contact layer is formed by depositing tin carbide doped with β element; β element is one or more of boron, aluminum, gallium, indium, and thallium; the β element doping amount is 0.1 to 1.0% by mass.

[0008] The deposition thickness of the back contact layer is 20–100 nm; the deposition method is magnetron sputtering, vapor deposition, or atomic layer deposition.

[0009] The substrate layer is a soda-lime glass or a borosilicate glass layer;

[0010] The transparent conductive oxide thin film layer is one or more of the following: F-doped tin oxide layer, In-doped zinc oxide layer, and Al-doped zinc oxide layer;

[0011] The high-resistivity buffer layer is SnO2, ZnO, α-doped ZnO, or an α-doped SnO2 layer, wherein the α element is one or more of Al, Zn, Mg, F, and Cd; the high-resistivity buffer layer is deposited by magnetron sputtering, chemical bath deposition, or thermal evaporation, and the deposition thickness is 5–100 nm.

[0012] The window layer is one or more of CdSe, CdS, CdSe:O, and CdS:O, and the deposition method is magnetron sputtering, chemical vapor deposition, or near-space sublimation, with a thickness of 30–300 nm.

[0013] The thickness of the cadmium telluride absorption layer is 1–10 μm, and the deposition method is near-space sublimation or vapor transport deposition.

[0014] The back electrode layer is deposited from one or more of aluminum, silver, gold, copper, nickel, and titanium, and the deposition method is magnetron sputtering, vapor deposition, or screen printing.

[0015] A method for fabricating a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer includes the following steps:

[0016] S1, Clean the glass substrate with a transparent conductive oxide film;

[0017] S2, a high-resistivity buffer layer is deposited on a transparent conductive oxide thin film by magnetron sputtering;

[0018] S3, deposited through a near-space sublimation window layer on a high-resistivity buffer layer;

[0019] S4, a cadmium telluride absorption layer is deposited on the window layer through near-space sublimation;

[0020] S5, depositing β-doped tin carbide on the cadmium telluride absorber layer to form a back contact layer; the β element is one or more of boron, aluminum, gallium, indium, and thallium; the β element doping amount is 0.1–1.0% by mass.

[0021] S6, thermally evaporate and deposit a back electrode layer on the back contact layer;

[0022] S5 uses β target and SnC target as magnetron sputtering sources, respectively. The power of the β target is maintained at 60-150W and the power of the SnC target is maintained at 60-120W. Argon gas is used as sputtering gas to generate sputtering plasma.

[0023] After magnetron sputtering deposition, the device is transferred to a 1–6 mM Cu substrate. 2+Soak in the solution for 1–5 minutes, then remove and dry with nitrogen gas.

[0024] The CdSe:O is CdSe doped with O element, and the CdS:O is CdS doped with O element, with the doping amount of O element being 0.1% to 1.0% by mass ratio.

[0025] The specific process of S1 is as follows:

[0026] After cutting the substrate glass with a transparent conductive oxide thin film layer, it is ultrasonically placed in acetone, ethanol, and deionized water in sequence, then dried with nitrogen gas, and then dried in an oven at 100°C for 10-20 minutes.

[0027] The specific process of S3 is as follows: a window layer is deposited by near-space sublimation, wherein the source temperature of the window layer material is 650°C and the substrate temperature is 500°C.

[0028] The specific process of S4 is as follows:

[0029] A cadmium telluride absorber layer was deposited on the window layer using a near-space sublimation method. Then, a 0.2–0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride absorber layer, and the layer was annealed in air at 388 °C for 30 min. The layer was then etched with a bromine-methanol solution for 2–5 min, rinsed with ultrapure water, and dried with nitrogen.

[0030] The specific process of S6 is as follows:

[0031] A gold back electrode layer is deposited above the back contact layer by thermal evaporation, and then the device is annealed in air at 150-200°C for 20-30 minutes.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] The present invention provides a cadmium telluride thin-film solar cell based on a tin-doped back contact layer and its fabrication method. Using tin carbide as the back contact layer provides good thermal stability; its performance remains stable after annealing at 200°C following metal back electrode deposition, without decomposition or significant chemical reactions or structural changes, thus ensuring long-term stable operation of the cell. Furthermore, doping the tin carbide with β-elements (p-type doping) allows the β-elements to occupy tin sites, transforming the tin carbide into a p-type semiconductor. This reduces the Schottky barrier between CdTe and the metal electrode, effectively preventing the diffusion of metal or impurities from the back electrode into the absorption layer and avoiding the formation of photogenerated carrier recombination centers. Additionally, the method involves immersion in Cu... 2+ Solution to introduce Cu 2+ Copper can occupy Cd sites to increase the P-type conductivity of CdTe, thereby improving hole mobility and transport efficiency.

[0034] The present invention provides a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer and a method for its fabrication. By doping the tin carbide back contact layer, the recombination of holes at the CdTe-metal electrode interface can be reduced, the hole collection and transport efficiency can be optimized, and the efficiency of the cadmium telluride thin-film solar cell can be improved. Attached Figure Description

[0035] Figure 1 This is a diagram of the layered structure of the solar cell according to the method of the present invention. Figure 2 This is a schematic diagram of the solar cell annealed at 200°C for half an hour according to the method of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] like Figure 1 As shown, a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer includes a substrate layer, a transparent conductive oxide thin film layer, a high-resistivity buffer layer, a window layer, a cadmium telluride absorber layer, a back contact layer, and a back electrode layer arranged sequentially.

[0038] The back contact layer is formed by depositing tin carbide doped with β element; β element is one or more of boron, aluminum, gallium, indium, and thallium; the β element doping amount is 0.1 to 1.0% by mass.

[0039] Furthermore, the deposition thickness of the back contact layer is 20–100 nm; the deposition method is magnetron sputtering, vapor deposition, or atomic layer deposition.

[0040] The back contact layer is also soaked in Cu. 2+ In a solution, Cu is introduced to occupy Cd sites to increase the p-type conductivity of CdTe.

[0041] Specifically, the substrate layer is a soda-lime glass or a borosilicate glass layer;

[0042] The transparent conductive oxide thin film layer is one or more of the following: F-doped tin oxide layer, In-doped zinc oxide layer, and Al-doped zinc oxide layer;

[0043] The high-resistance buffer layer is one or more of the following: tin oxide layer, zinc oxide layer, Mg-doped zinc oxide layer, and F-doped tin oxide layer;

[0044] The high-resistivity buffer layer is SnO2, ZnO, α-doped ZnO, or α-doped SnO2; the α element is one or more of Al, Zn, Mg, F, and Cd, and the deposition method is magnetron sputtering, chemical bath deposition, thermal evaporation, etc., with a deposition thickness of 5–100 nm.

[0045] The window layer is one or more of CdSe, CdS, CdSe:O, and CdS:O, and the deposition method is magnetron sputtering, chemical vapor deposition, near-space sublimation, etc., with a thickness of 30-300nm.

[0046] The CdSe:O is CdSe doped with O element, and the CdS:O is CdS doped with O element, wherein the doping amount of O element is 0.1% to 1.0% by mass ratio.

[0047] The cadmium telluride layer has a thickness of 1-10 μm and is deposited using near-space sublimation and vapor transport deposition methods.

[0048] The back contact layer is tin carbide doped with β element; β element is one or more of boron, aluminum, gallium, indium, and thallium, and the deposition method is magnetron sputtering, evaporation, atomic layer deposition, etc., with a deposition thickness of 20-100 nm;

[0049] The back electrode layer is formed by depositing one or more of aluminum, silver, gold, copper, nickel, and titanium, and the deposition method is magnetron sputtering, vapor deposition, screen printing, etc.

[0050] Furthermore, the method for fabricating the cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer includes the following operations:

[0051] S1, Clean the glass substrate with a transparent conductive oxide film;

[0052] S2, a high-resistivity buffer layer is deposited on a transparent conductive oxide thin film by magnetron sputtering;

[0053] S3, deposited through a near-space sublimation window layer on a high-resistivity buffer layer;

[0054] S4, a cadmium telluride absorption layer is deposited on the window layer through near-space sublimation;

[0055] S5, depositing β-doped tin carbide on the cadmium telluride absorber layer to form a back contact layer; the β element is one or more of boron, aluminum, gallium, indium, and thallium; the β element doping amount is 0.1 to 1.0% by mass.

[0056] S6, thermally evaporate and deposit a back electrode layer on the back contact layer;

[0057] S5 uses β target and SnC target as magnetron sputtering sources, respectively, with the power of β target maintained at 60-150W and the power of SnC target maintained at 60-120W, and argon gas is used as sputtering gas to generate sputtering plasma.

[0058] After magnetron sputtering deposition, the device is transferred to a 1–6 mM Cu substrate. 2+ Soak in the solution for 1–5 minutes, then remove and dry with nitrogen gas.

[0059] Specific implementation examples are given below.

[0060] Example 1

[0061] A method for fabricating a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer is as follows:

[0062] S1, cleaning of FTO substrate (commercially available): cut the glass substrate to an appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes, then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0063] S2, Preparation of high-resistivity buffer layer: A 10 nm thick SnO2 layer was deposited by magnetron sputtering;

[0064] S3, Preparation of the window layer: A CdS layer is deposited by near-space sublimation, wherein the CdS source temperature is 650℃, the substrate temperature is 500℃, and the thickness is 40nm;

[0065] S4, Preparation of the absorption layer: A 3 μm thick cadmium telluride layer was deposited on the window layer by near-space sublimation; then a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and annealed in air at 388 °C for 30 min, followed by etching with bromine-methanol solution for 2 min, and then rinsed with ultrapure water and dried with nitrogen.

[0066] S5, Preparation of the back contact layer: Boron-doped tin carbide film was deposited on the etched CdTe film by magnetron sputtering;

[0067] During the deposition process, high-purity (99.9%) boron targets and SnC (99.99%) targets were selected as sputtering sources to introduce boron elements for doping, with a boron doping ratio of 0.5%.

[0068] After the magnetron sputtering equipment is evacuated, the power of the boron target is maintained at 100W and the power of the SnC target is maintained at 100W. Argon (Ar) gas is used as the sputtering gas, and argon is mainly used to generate sputtering plasma.

[0069] The thin-film battery was immersed in a 3mM CuCl2 solution for 2 minutes to introduce copper ions (Cu). 2+ Copper can occupy Cd sites to increase the p-type conductivity of CdTe, thereby improving hole mobility and transport efficiency; immediately after soaking, dry with nitrogen gas;

[0070] S6, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 30 minutes to promote copper diffusion.

[0071] Example 2

[0072] Aluminum-doped tin carbide is used as a back buffer layer to fabricate high-efficiency cadmium telluride thin-film solar cells, as detailed below:

[0073] S1, Cleaning of IZO substrate: Cut the substrate glass into appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes. Then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0074] S2, Preparation of high-resistivity buffer layer: A 40nm thick Al-doped SnO2 layer was deposited by magnetron sputtering;

[0075] S3, Preparation of the window layer: A CdS:O layer is deposited by near-space sublimation, wherein the CdS:O source temperature is 650℃, the substrate temperature is 500℃, and the thickness is 40nm;

[0076] S4, Preparation of the absorption layer: A 3 μm thick cadmium telluride layer was deposited on the window layer by near-space sublimation; then a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and annealed in air at 388 °C for 30 min, followed by etching with bromine-methanol solution for 2 min, and then rinsed with ultrapure water and dried with nitrogen.

[0077] S5, Fabrication of the back contact layer: Aluminum-doped tin carbide film was deposited on the etched CdTe film by magnetron sputtering;

[0078] During the deposition process, high-purity (99.99%) Al target and SnC (99.99%) target were selected as sputtering sources to introduce Al element for doping, with an Al doping ratio of 0.1%.

[0079] The power of the Al target was maintained at 150W, and the power of the SnC target was maintained at 120W. Argon (Ar) gas was used as the sputtering gas, which was mainly used to generate sputtering plasma.

[0080] After deposition, the thin film device was immersed in a 3.8 mM CuCl2 solution for 2 min and then immediately dried with nitrogen gas.

[0081] S6, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 20 minutes to promote copper diffusion.

[0082] Example 3

[0083] The fabrication method of cadmium telluride thin-film solar cells based on tin carbide-doped back contact layers is as follows:

[0084] S1, Cleaning of ATO substrate: Cut the substrate glass to an appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes. Then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0085] S2, Preparation of high-resistivity buffer layer: A 50 nm thick F-doped SnO2 layer was deposited by magnetron sputtering;

[0086] S3, Preparation of the window layer: A CdSe layer is deposited by near-space sublimation, wherein the CdSe source temperature is 650℃, the substrate temperature is 500℃, and the thickness is 40nm;

[0087] S4, Preparation of the absorption layer: A 3 μm thick cadmium telluride layer was deposited on the window layer by near-space sublimation; then a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and annealed in air at 388 °C for 30 min, followed by etching with bromine-methanol solution for 2 min, and then rinsed with ultrapure water and dried with nitrogen.

[0088] S5, Fabrication of the back contact layer: A gallium-doped tin carbide film was deposited on the etched CdTe film by magnetron sputtering;

[0089] During the deposition process, high-purity (99.99%) Ga targets and SnC (99.99%) targets were selected as sputtering sources to introduce Ga elements for doping; the Ga doping ratio was 0.6%.

[0090] The power of the Ga target was maintained at 60W, and the power of the SnC target was maintained at 105W. Argon (Ar) gas was used as the sputtering gas, mainly to generate sputtering plasma.

[0091] After deposition, the film was immersed in a 2.6 mM CuCl2 solution for 5 min, and then immediately dried with nitrogen gas.

[0092] S6, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 30 minutes to promote copper diffusion.

[0093] Example 4

[0094] The fabrication method of cadmium telluride thin-film solar cells based on tin carbide-doped back contact layers is as follows:

[0095] S1, Cleaning of FTO substrate: Cut the substrate glass to an appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes. Then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0096] S2, Preparation of high-resistivity buffer layer: A 100 nm thick Cd-doped ZnO layer was deposited by magnetron sputtering;

[0097] S3, Preparation of the window layer: A CdSe:O layer is deposited by near-space sublimation, wherein the CdSe:O source temperature is 650℃, the substrate temperature is 500℃, and the thickness is 40nm;

[0098] S4, Preparation of the absorption layer: A 3 μm thick cadmium telluride layer was deposited on the window layer by near-space sublimation; then a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and annealed in air at 388 °C for 30 min, followed by etching with bromine-methanol solution for 2 min, and then rinsed with ultrapure water and dried with nitrogen.

[0099] S5, Fabrication of the back contact layer: Indium-doped tin carbide film was deposited on the etched CdTe film by magnetron sputtering;

[0100] During the deposition process, high-purity (99.99%) In target and SnC (99.99%) target were selected as sputtering sources to introduce In element for doping, with an In doping ratio of 1.0%.

[0101] The power of the In target was maintained at 120W, and the power of the SnC target was maintained at 60W. Argon (Ar) gas was used as the sputtering gas, which was mainly used to generate sputtering plasma.

[0102] After deposition, the film was immersed in a 2.4 mM CuSO4 solution for 3 min and then immediately dried with nitrogen gas.

[0103] S6, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 30 minutes to promote copper diffusion.

[0104] Example 5

[0105] The fabrication method of cadmium telluride thin-film solar cells based on tin carbide-doped back contact layers is as follows:

[0106] S1, Cleaning of FTO substrate: Cut the glass into appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes. Then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0107] S2, Preparation of high-resistivity buffer layer: A 40nm thick Mg-doped ZnO layer was deposited by magnetron sputtering;

[0108] S3, Preparation of the window layer: A CdS layer is deposited by near-space sublimation, wherein the CdS source temperature is 650℃, the substrate temperature is 500℃, and the thickness is 40nm;

[0109] S4, Preparation of the absorption layer: A 3 μm thick cadmium telluride layer was deposited on the window layer by near-space sublimation; then a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and annealed in air at 388 °C for 30 min, followed by etching with bromine-methanol solution for 2 min, and then rinsed with ultrapure water and dried with nitrogen.

[0110] S5, Fabrication of the back contact layer: A thallium-doped tin carbide film was deposited on the etched CdTe film by magnetron sputtering;

[0111] During the deposition process, high-purity (99.99%) and SnC (99.99%) targets were selected as sputtering sources to introduce Tl elements for doping, with a Tl doping ratio of 0.3%.

[0112] The power of the Tl target was maintained at 120W, and the power of the SnC target was maintained at 100W. Argon (Ar) gas was used as the sputtering gas, which was mainly used to generate sputtering plasma.

[0113] The film was immersed in a 5.4 mM CuCl2 solution for 1 min and then immediately dried with nitrogen gas.

[0114] S6, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 30 minutes to promote copper diffusion.

[0115] Comparative Example 1

[0116] The fabrication of cadmium telluride thin-film solar cells is detailed below:

[0117] S11, cleaning of FTO substrate: cut the glass into appropriate size, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 minutes, then blow it dry with high-purity nitrogen and dry it in a 100℃ oven for 20 minutes for later use.

[0118] S21, Preparation of high-resistivity buffer layer: A 40nm thick SnO2 layer was deposited by magnetron sputtering;

[0119] Preparation of S31, n-type window layer: An 80 nm thick cadmium selenide layer was deposited by magnetron sputtering;

[0120] S41, Preparation of the absorber layer: A 3 μm thick cadmium telluride layer was deposited on the window layer using a near-space sublimation method. Then, a 0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride film, and it was annealed in air at 388 °C for 30 min. Next, it was etched with a bromine-methanol solution for 2 min, rinsed with ultrapure water, and dried with nitrogen. The film was then immersed in a 5.8 mM CuCl2 solution for 2 min and immediately dried with nitrogen.

[0121] S51, Fabrication of the metal back electrode: A 100nm gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the battery device is annealed in air at 200°C for 30 minutes to promote copper diffusion.

[0122] The parameters of the cadmium telluride thin-film solar cells prepared in the examples and comparative examples are compared in Table 1.

[0123] Table 1 Performance parameters of cadmium telluride thin-film solar cells

[0124]

[0125] As shown in Table 1, the cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer provided by this invention can reduce hole recombination at the CdTe-metal electrode interface by using a tin carbide-doped back contact layer (p-type doping), thereby effectively collecting and transporting holes and improving the open-circuit voltage of the cell. It can also block the diffusion of metal or impurities in the back electrode to the absorption layer, avoiding the formation of photogenerated carrier recombination centers by metal diffusion, significantly reducing the contact barrier between cadmium telluride and the metal electrode, forming a good ohmic contact, thereby improving the cell performance: increasing the open-circuit voltage and photoelectric conversion efficiency of the cadmium telluride thin-film cell.

[0126] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer, characterized in that, It includes a substrate layer, a transparent conductive oxide thin film layer, a high-resistivity buffer layer, a window layer, a cadmium telluride absorber layer, a back contact layer, and a back electrode layer arranged sequentially. The back contact layer is formed by depositing tin carbide doped with β element; β element is one or more of boron, aluminum, gallium, indium and thallium; the β element doping amount is 0.1~1.0% by mass ratio.

2. The cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 1, characterized in that, The thickness of the back contact layer is 20~100nm; the deposition method is magnetron sputtering, vapor deposition or atomic layer deposition. The back contact layer is also soaked in Cu. 2+ In a solution, Cu is introduced to occupy Cd sites to increase the p-type conductivity of CdTe.

3. The cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 1, characterized in that, The substrate layer is a soda-lime glass or a borosilicate glass layer; The transparent conductive oxide thin film layer is one or more of the following: F-doped tin oxide layer, In-doped zinc oxide layer, and Al-doped zinc oxide layer; The high-resistivity buffer layer is SnO2, ZnO, α-doped ZnO, or an α-doped SnO2 layer, wherein the α element is one or more of Al, Zn, Mg, F, and Cd; the high-resistivity buffer layer is deposited by magnetron sputtering, chemical bath deposition, or thermal evaporation, and the deposition thickness is 5~100 nm. The window layer is one or more of CdSe, CdS, CdSe:O, and CdS:O, and the deposition method is magnetron sputtering, chemical vapor deposition, or near-space sublimation, with a thickness of 30~300nm. The thickness of the cadmium telluride absorption layer is 1~10µm, and the deposition method is near-space sublimation or vapor transport deposition. The back electrode layer is deposited from one or more of aluminum, silver, gold, copper, nickel, and titanium, and the deposition method is magnetron sputtering, vapor deposition, or screen printing.

4. The cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 3, characterized in that, The CdSe:O is CdSe doped with O element, and the CdS:O is CdS doped with O element, with the doping amount of O element being 0.1~1.0% by mass ratio.

5. A method for fabricating a cadmium telluride thin-film solar cell based on a tin carbide-doped back contact layer, characterized in that, Includes the following operations: S1, Clean the glass substrate with a transparent conductive oxide film; S2, a high-resistivity buffer layer is deposited on a transparent conductive oxide thin film by magnetron sputtering; S3, deposited through a near-space sublimation window layer on a high-resistivity buffer layer; S4, a cadmium telluride absorption layer is deposited on the window layer through near-space sublimation; S5, depositing β-doped tin carbide on the cadmium telluride absorber layer to form a back contact layer; the β element is one or more of boron, aluminum, gallium, indium, and thallium; the β element doping amount is 0.1~1.0% by mass. S6, thermally evaporate and deposit a back electrode layer on the back contact layer; S5 uses β target and SnC target as magnetron sputtering sources, respectively, with the power of β target maintained at 60~150W and the power of SnC target maintained at 60~120W, and argon gas is used as sputtering gas to generate sputtering plasma. After magnetron sputtering deposition, the device is transferred to 1-6 mM Cu. 2+ Soak in the solution for 1-5 minutes, then remove and dry with nitrogen gas.

6. The method for fabricating a cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 5, characterized in that, The specific process of S1 is as follows: After cutting the substrate glass with a transparent conductive oxide thin film layer, it is ultrasonically placed in acetone, ethanol, and deionized water in sequence, then dried with nitrogen gas, and then dried in an oven at 100°C for 10-20 minutes.

7. The method for fabricating a cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 5, characterized in that, The specific process of S3 is as follows: a window layer is deposited by near-space sublimation, wherein the source temperature of the window layer material is 650°C and the substrate temperature is 500°C.

8. The method for fabricating a cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 5, characterized in that, The specific process of S4 is as follows: A cadmium telluride absorber layer was deposited on the window layer using a near-space sublimation method. Then, a 0.2-0.5 mol / L CdCl2 aqueous solution was sprayed onto the cadmium telluride absorber layer, and the layer was annealed in air at 388°C for 30 min. Next, the layer was etched with a bromine-methanol solution for 2-5 min, rinsed with ultrapure water, and dried with nitrogen.

9. The method for fabricating a cadmium telluride thin-film solar cell based on a doped tin carbide back contact layer as described in claim 5, characterized in that, The specific process of S6 is as follows: A gold back electrode layer is deposited on top of the back contact layer by thermal evaporation, and then the device is annealed in air at 150~200℃ for 20~30 min.

Images