A cadmium telluride thin-film solar cell based on a p-type copper-containing oxide back contact layer and a preparation method thereof

Abstract

This invention discloses a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer and its fabrication method, belonging to the field of solar cell technology. The cadmium telluride thin-film solar cell comprises, from bottom to top, a transparent conductive oxide thin film layer, a high-resistivity buffer layer, an n-type cell window layer, a p-type cell absorber layer, a back contact layer, and a back electrode layer; the back contact layer is made of CuMO2 material; wherein M is one or more of Al, Ga, In, Sc, and Y. This invention uses a p-type copper oxide thin film as the back contact layer, which can reflect photogenerated electrons at the cadmium telluride back surface to the PN junction, greatly reducing electron recombination at the cadmium telluride back surface, improving hole transport capability, and avoiding complex copper doping post-processing, thereby improving the open-circuit voltage and conversion efficiency of the cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and in particular relates to a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer and its preparation method. Background Technology

[0002] Cadmium telluride (CdTe) thin-film solar cells are considered one of the most promising types of solar cells. CdTe exhibits properties exceeding 5 × 10⁻⁶. 5 cm -1 Its high absorption coefficient and 1.5 eV direct band gap are very well matched with the distribution of the solar spectrum on the ground, making it a solar cell material that can absorb most photons in the visible light range, thus maximizing the conversion of solar energy into electrical energy.

[0003] The most critical aspect of fabricating high-performance CdTe thin-film solar cells is the formation of the back contact layer. Directly contacting the metal to the CdTe absorber surface makes it impossible to form an ohmic contact and severely hinders the efficient transport of photogenerated carriers, thus limiting the overall performance of the cell. Therefore, a material with a lower valence band offset and a higher conduction band offset compared to CdTe must be inserted between the CdTe absorber layer and the metal back electrode. This contact material generates an electronic barrier, resulting in a higher cell voltage, especially for a relatively thin absorber layer.

[0004] Currently, ZnTe is the main material used to achieve back contacts, but its disadvantage is that it relies on copper doping to function. This is usually achieved by using copper-containing layers or copper-doped zinc telluride. The introduction of copper may generate free Cu ions, which not only cause lattice distortion and increased interface state density in the CdTe absorber layer, exacerbating carrier recombination losses, but also lead to interface contact failure between the back contact layer and the absorber layer and the back electrode layer due to the migration and enrichment of Cu ions inside the device, significantly reducing the long-term stability and lifespan of the battery. At the same time, the copper doping post-processing steps are complicated, and the control of parameters such as doping concentration and annealing temperature requires strict precision, which can easily lead to poor performance consistency between batches of devices, increasing the process cost and yield loss of large-scale production. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer and its fabrication method. This invention uses p-type copper oxide CuMO2 as the back contact layer. Copper exists stably in the intrinsic crystal structure of the oxide in a lattice form, without the generation of free Cu ions. This fundamentally avoids the series of problems caused by copper doping in traditional ZnTe. Furthermore, the material itself is a p-type semiconductor with excellent hole transport capability and electron blocking characteristics, eliminating the need for additional copper doping and subsequent modification. This simplifies the fabrication process, reduces production control difficulties, and achieves efficient carrier transport and low recombination loss. Simultaneously, the stable lattice structure allows the cell to possess both high photoelectric conversion performance and excellent long-term stability, perfectly meeting the application requirements of high performance, low cost, and large-scale production of CdTe thin-film solar cells.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer, comprising a transparent conductive oxide thin film layer, a high-resistivity buffer layer, an n-type cell window layer, a p-type cell absorber layer, a back contact layer, and a back electrode layer stacked sequentially; wherein the back contact layer is a p-type copper oxide layer, and the p-type copper oxide is CuMO2; wherein M is one or more of Al, Ga, In, Sc, and Y.

[0007] This invention prepares a p-type copper oxide layer on the absorber layer of a CdTe solar cell. This not only eliminates the need for a complex subsequent copper doping process, but also blocks electron transport, improves hole transport capacity, reduces carrier recombination loss at the interface, and thus improves the open-circuit voltage of the battery device and the overall performance of the battery.

[0008] Furthermore, the thickness of the high-resistivity buffer layer is 30-80 nm; the thickness of the n-type battery window layer is 80-100 nm; the thickness of the p-type battery absorption layer is 3-4 µm; the thickness of the back contact layer is 50 nm; and the thickness of the back electrode layer is 100 nm.

[0009] Furthermore, the transparent conductive oxide thin film layer is selected from F-doped tin oxide layer, In-doped zinc oxide layer, or Al-doped zinc oxide layer.

[0010] Furthermore, the high-resistivity buffer layer is selected from ZnO layer, SnO2 layer, A-doped ZnO layer or A-doped SnO2 layer, wherein the A element is selected from Al, Zn, Mg, F or Cd.

[0011] Furthermore, the n-type battery window layer is selected from cadmium selenide layer, cadmium sulfide layer, oxygen-doped cadmium selenide layer, or oxygen-doped cadmium sulfide layer.

[0012] Furthermore, the p-type battery absorber layer is selected from cadmium telluride layers.

[0013] Furthermore, the back electrode layer is selected from aluminum, silver, gold, copper, nickel, or titanium back electrode layers.

[0014] Secondly, the present invention provides a method for preparing a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer, comprising the following steps: S1. Clean the conductive substrate to obtain a transparent conductive oxide thin film layer; S2. Deposit a high-resistivity buffer layer on the transparent conductive oxide thin film layer; S3. Deposit an n-type battery window layer on the high-resistivity buffer layer; S4. Deposit a p-type battery absorption layer on the n-type battery window layer; S5. A back contact layer is deposited on the p-type battery absorption layer by magnetron sputtering; S6. Deposit a back electrode layer on the back contact layer; S7. Anneal the device prepared in S6 to obtain the cadmium telluride thin-film solar cell based on the p-type copper oxide back contact layer.

[0015] Furthermore, the annealing treatment is performed at a temperature of 260 °C for 60 s.

[0016] Furthermore, the deposition in step S2 is selected from magnetron sputtering deposition, chemical bath deposition, or thermal evaporation deposition; The deposition described in step S3 is selected from magnetron sputtering deposition, chemical vapor deposition, or near-space sublimation deposition; The deposition described in step S4 is selected from near-space sublimation deposition or gas transport deposition; The deposition process described in step S5 is selected from pulsed laser deposition, magnetron sputtering deposition, or thermal evaporation deposition. The deposition in step S6 is selected from magnetron sputtering deposition, vapor deposition or screen printing deposition.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer. The p-type copper oxide thin film is used as the back contact layer, which can reflect photogenerated electrons at the cadmium telluride back surface to the PN junction, greatly reducing electron recombination at the cadmium telluride back surface, improving hole transport capability, and avoiding complex copper doping post-processing, thereby improving the open-circuit voltage and conversion efficiency of the cell. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer prepared according to the present invention. Figure 2 The current density-voltage (JV) characteristic curves of the cadmium telluride thin-film solar cells based on the p-type copper oxide back contact layer prepared in Examples 1-4 and the cadmium telluride thin-film solar cells prepared in Comparative Example 1 are shown. Figure 3 The graphs show the stability test results of the cadmium telluride thin-film solar cells prepared in Example 3 and Comparative Example 1 under aging conditions of 85°C and 85% relative humidity. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] The room temperature in this invention refers to 25±2℃.

[0026] Example 1: A cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer. In this embodiment, cadmium telluride thin-film solar cells are fabricated using CuAlO2 as the back contact layer. The specific steps are as follows: S1. Cleaning of FTO substrate: Cut FTO (fluorine-doped tin oxide) conductive glass into appropriate sizes, then place it in acetone, ethanol and deionized water in sequence and sonicate for 20 min, then blow it dry with high-purity nitrogen gas, and dry it in an oven at 100℃ for 20 min to prepare a transparent conductive oxide thin film layer for later use. S2. Preparation of high-resistivity buffer layer: A 30 nm thick SnO2 layer was deposited on the S1-treated FTO substrate by magnetron sputtering. SnO2 target was used as sputtering source, sputtering power was set to 120 W, and argon and oxygen were used as sputtering gases. The argon gas flow rate was 50 sccm, the oxygen gas flow rate was 2 sccm, and the working pressure was 0.4 Pa. Preparation of the window layer of S3.n type battery: An 80nm thick cadmium selenide layer was deposited by near-space sublimation method; wherein, cadmium selenide was selected as the source material for near-space sublimation deposition, the vacuum degree in the deposition chamber was 2000Pa, the source material temperature was set to 680℃, the substrate temperature was 650℃, and the deposition time was 30s. Preparation of the absorber layer for the S4 p-type battery: A 3µm thick cadmium telluride layer was deposited on the n-type battery window layer using a near-space sublimation method. The cadmium telluride film was then immersed in a 0.02g / mL CdCl2 aqueous solution for 10s to etch the p-type battery absorber layer. After drying with compressed air, the layer was treated at 400℃ for 30min in a nitrogen atmosphere, rinsed with ultrapure water, and dried. Cadmium telluride was selected as the source material for the near-space sublimation deposition method. The vacuum degree in the deposition chamber was 2000Pa, the source material temperature was set to 700℃, the substrate temperature was 660℃, and the deposition time was 5min. S5. Preparation of back contact layer: A CuAlO2 thin film was deposited on the etched cadmium telluride absorber layer by magnetron sputtering. A high-purity (99.9%) CuAlO2 target was selected as the sputtering source, the sputtering power was set to 80W, and argon and oxygen were used as sputtering gases. Argon was mainly used to generate sputtering plasma, and oxygen was used to ensure the oxygen content in the film. The argon-oxygen ratio was kept at 3:2 using a flow meter. The working pressure was 0.7Pa, and the final film thickness was 50nm. S6. Fabrication of the metal back electrode: A 100 nm metal back electrode layer is deposited above the back contact layer; S7. Annealing treatment: The battery device obtained in S6 is annealed at 260°C for 60s to prepare a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer.

[0027] Example 2: A cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer. In this embodiment, cadmium telluride thin-film solar cells are fabricated using CuGaO2 as the back contact layer. The specific steps are as follows: S1. Same as Example 1; S2. Preparation of high-resistivity buffer layer: An 80 nm thick SnO2 layer was deposited on the S1-treated FTO substrate by magnetron sputtering. SnO2 target was used as sputtering source, sputtering power was set to 120 W, and argon and oxygen were used as sputtering gases. The argon gas flow rate was 50 sccm, the oxygen gas flow rate was 2 sccm, and the working pressure was 0.4 Pa. Preparation of the window layer of S3.n type battery: An 80nm thick cadmium selenide layer was deposited by near-space sublimation method; wherein, cadmium selenide was selected as the source material for near-space sublimation deposition, the vacuum degree in the deposition chamber was 2000Pa, the source material temperature was set to 680℃, the substrate temperature was 650℃, and the deposition time was 30s. Preparation of the absorber layer for the S4 p-type battery: A 3µm thick cadmium telluride layer was deposited on the n-type battery window layer using a near-space sublimation method. The cadmium telluride film was then immersed in a 0.02g / mL CdCl2 aqueous solution for 10s to etch the p-type battery absorber layer. After drying with compressed air, the layer was treated at 400℃ for 30min in a nitrogen atmosphere, rinsed with ultrapure water, and dried. Cadmium telluride was selected as the source material for the near-space sublimation deposition method. The vacuum degree in the deposition chamber was 2000Pa, the source material temperature was set to 700℃, the substrate temperature was 660℃, and the deposition time was 5min. S5. Preparation of back contact layer: A CuGaO2 thin film was deposited on the etched cadmium telluride absorber layer by magnetron sputtering. A high-purity (99.9%) CuGaO2 target was used as the sputtering source, the sputtering power was set to 80W, argon and oxygen were used as sputtering gases, the argon-oxygen ratio was kept at 3:2 by a flow meter, the working pressure was 0.7Pa, and the final film thickness was 50nm. S6-S7: Same as Example 1; Example 3: A cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer. This embodiment uses CuInO2 as the back contact layer to prepare a cadmium telluride thin-film solar cell. The specific steps are as follows: S1. Same as Example 1; S2. Preparation of high-resistivity buffer layer: A 30 nm thick SnO2 layer was deposited on the S1-treated FTO substrate by magnetron sputtering. SnO2 target was used as sputtering source, sputtering power was set to 120 W, and argon and oxygen were used as sputtering gases. The argon gas flow rate was 50 sccm, the oxygen gas flow rate was 2 sccm, and the working pressure was 0.4 Pa. Preparation of the window layer of S3.n type battery: A 100 nm thick cadmium selenide layer was deposited by near-space sublimation method; wherein, cadmium selenide was selected as the source material for near-space sublimation deposition, the vacuum degree in the deposition chamber was 2000 Pa, the source material temperature was set to 680℃, the substrate temperature was 650℃, and the deposition time was 45 s. Preparation of the absorber layer of the S4 p-type battery: A 4 µm thick cadmium telluride layer was deposited on the window layer of the n-type battery by near-space sublimation. Then, the cadmium telluride film was immersed in a 0.02 g / mL CdCl2 aqueous solution for 10 s to etch the absorber layer of the p-type battery. After drying with compressed air, it was treated at 400 °C for 30 min in a nitrogen atmosphere, rinsed with ultrapure water, and dried. Among them, cadmium telluride was selected as the source material for near-space sublimation deposition. The vacuum degree in the deposition chamber was 2000 Pa, the source material temperature was set at 700 °C, the substrate temperature was 660 °C, and the deposition time was 6 min. S5. Preparation of back contact layer: A CuInO2 thin film was deposited on the etched cadmium telluride absorber layer by magnetron sputtering. A high-purity (99.9%) CuInO2 target was used as the sputtering source, the sputtering power was set to 80W, argon and oxygen were used as sputtering gases, the argon-oxygen ratio was kept at 3:2 by a flow meter, the working pressure was 0.7Pa, and the final film thickness was 50nm. S6-S7: Same as Example 1; Example 4: A cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer. This embodiment uses CuScO2 as the back contact layer to prepare a cadmium telluride thin-film solar cell. The specific steps are as follows: S1. Same as Example 1; S2. Preparation of high-resistivity buffer layer: A 30 nm thick SnO2 layer was deposited on the S1-treated FTO substrate by magnetron sputtering. SnO2 target was used as sputtering source, sputtering power was set to 120 W, and argon and oxygen were used as sputtering gases. The argon gas flow rate was 50 sccm, the oxygen gas flow rate was 2 sccm, and the working pressure was 0.4 Pa. Preparation of the window layer of S3.n type battery: A 100 nm thick cadmium selenide layer was deposited by near-space sublimation method; wherein, cadmium selenide was selected as the source material for near-space sublimation deposition, the vacuum degree in the deposition chamber was 2000 Pa, the source material temperature was set to 680℃, the substrate temperature was 650℃, and the deposition time was 45 s. Preparation of the absorber layer of the S4 p-type battery: A 4 µm thick cadmium telluride layer was deposited on the window layer of the n-type battery by near-space sublimation. Then, the cadmium telluride film was immersed in a 0.02 g / mL CdCl2 aqueous solution for 10 s to etch the absorber layer of the p-type battery. After drying with compressed air, it was treated at 400 °C for 30 min in a nitrogen atmosphere, rinsed with ultrapure water, and dried. Among them, cadmium telluride was selected as the source material for near-space sublimation deposition. The vacuum degree in the deposition chamber was 2000 Pa, the source material temperature was set at 700 °C, the substrate temperature was 660 °C, and the deposition time was 6 min. S5. Preparation of back contact layer: A CuScO2 thin film was deposited on the etched cadmium telluride absorber layer by magnetron sputtering. A high-purity (99.9%) CuScO2 target was used as the sputtering source, the sputtering power was set to 80W, argon and oxygen were used as sputtering gases, the argon-oxygen ratio was kept at 3:2 by a flow meter, the working pressure was 0.7Pa, and the final film thickness was 50nm. S6-S7: Same as Example 1.

[0028] Figure 1 This is a schematic diagram of the structure of the cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer prepared according to the present invention.

[0029] Comparative Example 1 This comparative example uses Cu as the back contact layer to prepare a cadmium telluride thin-film solar cell. The specific steps are as follows: S1-S4: Same as in Example 1; S5. Preparation of back contact layer: A Cu thin film was deposited on the etched cadmium telluride absorber layer by magnetron sputtering. A high-purity (99.99%) Cu target was used as the sputtering source, the power was set to 80 W, and argon was used as the sputtering gas. Argon was mainly used to generate sputtering plasma. The working pressure was 0.7 Pa. The final film thickness was 50 nm. S6-S7: Same as Example 1; Table 1 shows the cell performance parameters of the cadmium telluride thin-film solar cells prepared in Examples 1-4 and Comparative Example 1. Figure 2 The current density-voltage (JV) characteristic curves are shown for the cadmium telluride thin-film solar cells based on p-type copper oxide back contact layers prepared in Examples 1-4 and the cadmium telluride thin-film solar cells prepared in Comparative Example 1. Figure 3 The graphs show the stability test results of the cadmium telluride thin-film solar cells prepared in Example 3 and Comparative Example 1 under aging conditions of 85°C and 85% relative humidity. The open-circuit voltage is the terminal voltage of the cell in the no-load (open-circuit) state. The open-circuit voltage reflects the built-in electric field strength and carrier separation efficiency of the cell. A higher open-circuit voltage indicates a stronger internal electric field, better separation of photogenerated carriers (electron-hole pairs), and lower recombination losses. The short-circuit current is the output current of the cell in the short-circuit state (load resistance is 0). The short-circuit current reflects the cell's ability to collect photogenerated carriers. A larger short-circuit current indicates a higher solar energy absorption efficiency and lower carrier (especially electron) transport loss from the absorber layer to the electrodes. The fill factor is the ratio of the battery's maximum output power to the product of the short-circuit current density and open-circuit voltage. It reflects the squareness of the battery's output characteristics, i.e., how close the actual power is to the theoretical maximum power. A higher fill factor indicates a smaller series resistance (e.g., electrode contact resistance, absorber layer bulk resistance) and a larger parallel resistance (e.g., lower leakage current), resulting in less power conversion efficiency loss. Photoelectric conversion efficiency (PCE) is the ratio of the battery's maximum output power to the incident light power. It is a core indicator of a battery's overall performance, directly reflecting its ability to convert solar energy into electrical energy. A higher PCE indicates less energy loss.

[0030] Table 1 As shown in Table 1 and Figure 2 As shown, after the introduction of the new back contact layer, the current density and fill factor of the battery are significantly improved, thereby improving the photoelectric conversion efficiency of the battery device.

[0031] like Figure 3As shown, after introducing the new back contact layer, the battery stability improved from 80.00% in Comparative Example 1 to 95.26% in Example 3. This invention, through the design of a p-type copper oxide CuMO2 back contact layer, fundamentally avoids the problem of free Cu diffusion in traditional back contact layers. Combined with parameter optimization of the magnetron sputtering process, this results in excellent long-term battery stability.

[0032] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer, characterized in that, It includes a transparent conductive oxide thin film layer, a high-resistivity buffer layer, an n-type battery window layer, a p-type battery absorption layer, a back contact layer, and a back electrode layer stacked sequentially; the back contact layer is a p-type copper-containing oxide layer, and the p-type copper-containing oxide is CuMO2; wherein M is one or more of Al, Ga, In, Sc, and Y.

2. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The thickness of the high-resistivity buffer layer is 30-80 nm; the thickness of the n-type battery window layer is 80-100 nm; the thickness of the p-type battery absorption layer is 3-4 µm; the thickness of the back contact layer is 50 nm; and the thickness of the back electrode layer is 100 nm.

3. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The transparent conductive oxide thin film layer is selected from F-doped tin oxide layer, In-doped zinc oxide layer or Al-doped zinc oxide layer.

4. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The high-resistivity buffer layer is selected from ZnO layer, SnO2 layer, A-doped ZnO layer or A-doped SnO2 layer, wherein the A element is selected from Al, Zn, Mg, F or Cd.

5. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The n-type battery window layer is selected from cadmium selenide layer, cadmium sulfide layer, oxygen-doped cadmium selenide layer, or oxygen-doped cadmium sulfide layer.

6. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The p-type battery absorber layer is selected from cadmium telluride.

7. The cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer according to claim 1, characterized in that, The back electrode layer is selected from aluminum, silver, gold, copper, nickel, or titanium back electrode layers.

8. A method for preparing a cadmium telluride thin-film solar cell based on a p-type copper oxide back contact layer as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Clean the conductive substrate to obtain a transparent conductive oxide thin film layer; S2. Deposit a high-resistivity buffer layer on the transparent conductive oxide thin film layer; S3. Deposit an n-type battery window layer on the high-resistivity buffer layer; S4. Deposit a p-type battery absorption layer on the n-type battery window layer; S5. A back contact layer is deposited on the p-type battery absorption layer by magnetron sputtering; S6. Deposit a back electrode layer on the back contact layer; S7. Anneal the device prepared in S6 to obtain the cadmium telluride thin-film solar cell based on the p-type copper oxide back contact layer.

9. The preparation method according to claim 8, characterized in that, The annealing process in step S7 is performed at a temperature of 260°C for 60 seconds.

10. The preparation method according to claim 8, characterized in that, The deposition method described in step S2 is selected from magnetron sputtering deposition, chemical bath deposition, or thermal evaporation deposition; The deposition described in step S3 is selected from magnetron sputtering deposition, chemical vapor deposition, or near-space sublimation deposition; The deposition described in step S4 is selected from near-space sublimation deposition or gas transport deposition; The deposition process described in step S5 is selected from pulsed laser deposition, magnetron sputtering deposition, or thermal evaporation deposition. The deposition in step S6 is selected from magnetron sputtering deposition, vapor deposition or screen printing deposition.

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