Copper vanadium sulfur selenium light-absorbing thin film and preparation method and application thereof

Abstract

This invention proposes a copper-vanadium-sulfur-selenium (Cvanadium-sulfur-selenium) light-absorbing thin film, its preparation method, and its application. Addressing the problems of small grain size and insufficient density in existing Cvanadium-sulfur-selenium light-absorbing thin films, this invention utilizes optimized selenization conditions and metal cation doping techniques to prepare Cvanadium-sulfur-selenium light-absorbing thin films. Optimized selenization conditions result in Cvanadium-sulfur-selenium light-absorbing thin films with larger grain sizes and reduced surface porosity, significantly improving the film's quality. Doping with metal cations such as sodium, bismuth, and cadmium ions promotes grain growth, increasing grain size and / or reducing film porosity, which is beneficial for improving cell conversion efficiency. This method improves film quality, and applying the prepared Cvanadium-sulfur-selenium light-absorbing thin film to the light-absorbing layer of a solar cell enhances the photoelectric conversion efficiency of the Cvanadium-sulfur-selenium light-absorbing thin film solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar energy light-absorbing layer material technology, specifically relating to copper vanadium sulfur selenide light-absorbing thin films, their preparation methods, and applications. Background Technology

[0002] Thin-film solar cells have seen rapid development due to their low manufacturing cost, simple fabrication process, and stable performance. Major thin-film solar cells include cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and copper zinc tin sulfide selenide (CZTSSe). However, the extremely low abundance of Te, Ga, and In elements in the Earth's crust, coupled with the highly toxic nature of Cd, limits the large-scale development of CdTe and CIGS. Furthermore, copper zinc tin sulfide selenide suffers from several inherent defects (Cu... Zn Sn Zn ) and defect clusters (2Cu Zn +Sn Zn The limitations imposed by these factors restrict the improvement of the open-circuit voltage of the device, making it difficult to improve the device's efficiency. Researchers have proposed a new ternary copper chalcogenide semiconductor, Cu3MCh4 (M = V, Nb, Ta; Ch = S, Se, Te), which has been proven to be a P-type semiconductor. The optical band gaps of Cu3VS4 and Cu3VSe4 are 1.72 eV and 1.49 eV, respectively, matching sunlight. Furthermore, the conduction band bottom structure of this material is determined by V3d, and the calculated valence band top energy is very high, with electrons approaching a vacuum, making it easier to generate holes. Therefore, it exhibits good P-type mobility and can be used in photovoltaic applications.

[0003] However, the preparation methods for Cu3V(S,Se)4 are not yet perfect, and high-quality Cu3V(S,Se)4 thin films cannot be prepared. Therefore, the photoelectric conversion efficiency of solar cells using Cu3V(S,Se)4 as the light-absorbing layer has not reached an ideal level. Currently, there are many methods for preparing thin-film solar cells, among which the solution method is one of the most widely used methods due to its safety, low cost, and simplicity. Chinese patent CN117995930B discloses a method for preparing copper vanadium sulfur selenide Cu3V(S,Se)4 material using an amine-thiol system. However, the small grain size and numerous pores in its light-absorbing layer remain the primary factors limiting cell performance. Therefore, an optimization scheme is proposed to improve the quality of the Cu3V(S,Se)4 light-absorbing layer in order to improve solar cell performance. Summary of the Invention

[0004] The first objective of this invention is to address the problem of low quality in existing copper-vanadium-sulfur-selenium thin films by proposing a novel method for preparing copper-vanadium-sulfur-selenium light-absorbing thin films, which optimizes selenization conditions and incorporates trace elements.

[0005] The second objective of this invention is to provide copper-vanadium-sulfur-selenium thin films with higher quality, larger grain size, and fewer surface pores.

[0006] The third objective of this invention is to provide the application of copper vanadium sulfur selenide thin films in the preparation of solar cells, resulting in solar cells with high photoelectric conversion efficiency.

[0007] The first objective of this invention is achieved by the following technical solution:

[0008] A method for improving the quality of copper vanadium sulfur selenide thin films by optimizing selenization conditions is as follows.

[0009] A method for preparing a copper-vanadium-sulfur-selenium light-absorbing thin film includes steps A to E; Step A: adding mercaptoacetic acid and ethanolamine to a reaction vessel and stirring to obtain a molecular solution; Step B: adding a copper source and a vanadium source to the molecular solution and reacting until the copper source and the vanadium source are completely dissolved to obtain a mixed solution; Step C: adding a sulfur source and ethylene glycol methyl ether to the mixed solution, wherein the volume ratio of ethylene glycol methyl ether to mercaptoacetic acid and the ethanolamine is (3~7):(1~3):(1~4), preferably 5:1:2, and reacting until the sulfur source is completely dissolved to obtain a copper-vanadium-sulfur precursor solution; Step D: spin-coating and sintering the copper-vanadium-sulfur precursor solution to obtain a copper-vanadium-sulfur thin film; Step E: adding a selenium source to the copper-vanadium-sulfur thin film and covering the copper-vanadium-sulfur thin film with a 1 During the high-temperature selenization process, sodium in a mm-thick soda-lime glass diffuses to the grain boundaries of CVSSe, reducing the surface energy of the grain boundaries and enhancing grain growth, ultimately resulting in a denser CVSSe film. The selenization reaction yields a copper vanadium sulfur selenide film with large grains. The selenization temperature is 510–550 °C, and the reaction time is 10–90 min (preferably, the selenization temperature is 530 °C, and the reaction time is 70 min; the selenization reaction can be a one-step, two-step, or three-step selenization method). By optimizing the selenization conditions, the elemental distribution within the film is made more uniform, resulting in a denser CVSSe film. Simultaneously, larger Se atoms replace some smaller S atoms, increasing the grain size. This helps reduce surface defects and on-voltage losses in devices. Therefore, by optimizing the refining conditions, a light-absorbing layer film with larger grain size can be prepared. Furthermore, the porosity of the film surface is reduced, significantly improving the quality of the copper vanadium sulfur selenide film.

[0010] In step B, the copper source is one or more of elemental copper, copper salt, copper oxide, cuprous oxide, and copper acetate, preferably copper acetate; the vanadium source is vanadium acetylacetonate and / or vanadium pentoxide, preferably vanadium acetylacetonate; the sulfur source in step C is thiourea and / or sulfur powder, preferably thiourea; and the selenium source in step E is one or more of selenium powder, selenium granules, selenium dioxide, and selenium disulfide.

[0011] Further, in step A, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step B, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step C, the reaction temperature is 0~20℃, preferably 0℃, and the time is 30~120min, preferably 60min; in step D, the sintering temperature is 300~320℃, preferably 300℃, and the time is 1.5~6min, preferably 2min, and the spin coating and sintering process is repeated 4~10 times, preferably 7 times.

[0012] A method for improving the quality of copper-vanadium-sulfur-selenium thin films by doping with trace elements is described below.

[0013] A method for preparing a copper-vanadium-sulfur-selenium light-absorbing thin film includes steps S1 to S5; step S1: adding mercaptoacetic acid and ethanolamine to a reaction vessel and stirring to obtain a molecular solution; step S2: adding a copper source and a vanadium source to the molecular solution and reacting until the copper source and the vanadium source are completely dissolved to obtain a mixed solution; step S3: adding a sulfur source, a metal cation, and ethylene glycol methyl ether to the mixed solution, wherein the volume ratio of ethylene glycol methyl ether to mercaptoacetic acid and the ethanolamine is (3~7):(1~3):(1~4), preferably 5:1:2, and the molar ratio of the metal cation doping is ≤1%; after reacting until the sulfur source is completely dissolved, a copper-vanadium-sulfur precursor solution is obtained; step S4: spin-coating and sintering the copper-vanadium-sulfur precursor solution to obtain a copper-vanadium-sulfur thin film; step S5: adding a selenium source to the copper-vanadium-sulfur thin film obtained in step S4 and performing a selenization reaction to obtain a copper-vanadium-sulfur-selenium thin film doped with metal cations and having large grains.

[0014] In step S2, the copper source is one or more of elemental copper, copper salt, copper oxide, cuprous oxide, and copper acetate, preferably copper acetate; the vanadium source is vanadium acetylacetonate and / or vanadium pentoxide, preferably vanadium acetylacetonate; in step S3, the sulfur source is thiourea and / or sulfur powder, preferably thiourea; and in step S5, the selenium source is one or more of selenium powder, selenium granules, selenium dioxide, and selenium disulfide.

[0015] Furthermore, the metal cation includes at least one of sodium ions, cadmium ions, and bismuth ions.

[0016] Further, in step S1, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step S2, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step S3, the reaction temperature is 0~20℃, preferably 0℃, and the time is 30~120min, preferably 60min; in step S4, the sintering temperature is 300~320℃, preferably 300℃, and the time is 1.5~6min, preferably 2min, and the spin coating and sintering process is repeated 4~10 times, preferably 7 times; in step S5, the selenization temperature of the selenization reaction is 350~560℃, the reaction time is 10~90min, and the selenization reaction is a one-step selenization method, a two-step selenization method, or a three-step selenization method.

[0017] A method for improving the quality of copper vanadium sulfur selenide thin films by optimizing selenization conditions and doping with trace elements is described below.

[0018] A method for preparing a copper-vanadium-sulfur-selenium light-absorbing thin film includes steps P1 to P5; Step P1: adding mercaptoacetic acid and ethanolamine to a reaction vessel and stirring to obtain a molecular solution; Step P2: adding a copper source and a vanadium source to the molecular solution and reacting until the copper source and the vanadium source are completely dissolved to obtain a mixed solution; Step P3: adding a sulfur source, a metal cation, and ethylene glycol methyl ether to the mixed solution, wherein the volume ratio of ethylene glycol methyl ether to mercaptoacetic acid and the ethanolamine is (3~7):(1~3):(1~4), preferably 5:1:2, and the molar ratio of the metal cation doping is ≤1%; after reacting until the sulfur source is completely dissolved, a copper-vanadium-sulfur precursor solution is obtained; Step P4: spin-coating and sintering the copper-vanadium-sulfur precursor solution to obtain a copper-vanadium-sulfur thin film; Step P5: adding a selenium source to the copper-vanadium-sulfur thin film obtained in Step P4 and covering the copper-vanadium-sulfur thin film with a 1 A copper-vanadium-sulfur-selenium thin film with large grains is obtained by performing a selenization reaction on a mm-thick soda-lime glass. The selenization reaction is carried out at a temperature of 510~550℃ and a reaction time of 10~90min (preferably, the selenization temperature is 530℃ and the reaction time is 70min; the selenization reaction is carried out by a one-step selenization method, a two-step selenization method or a three-step selenization method).

[0019] In step P2, the copper source is one or more of elemental copper, copper salt, copper oxide, cuprous oxide, and copper acetate, preferably copper acetate; the vanadium source is vanadium acetylacetonate and / or vanadium pentoxide, preferably vanadium acetylacetonate; in step P3, the sulfur source is thiourea and / or sulfur powder, preferably thiourea; and in step P5, the selenium source is one or more of selenium powder, selenium granules, selenium dioxide, and selenium disulfide.

[0020] Furthermore, the metal cation includes at least one of sodium ions, cadmium ions, and bismuth ions.

[0021] Further, in step P1, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step P2, the reaction temperature is 60~100℃, preferably 70℃, and the time is 10~60min, preferably 30min; in step P3, the reaction temperature is 0~20℃, preferably 0℃, and the time is 30~120min, preferably 60min; in step P4, the sintering temperature is 300~320℃, preferably 300℃, and the time is 1.5~6min, preferably 2min, and the spin coating and sintering process is repeated 4~10 times, preferably 7 times.

[0022] The second objective of this invention is achieved by the following technical solution:

[0023] The copper-vanadium-sulfur-selenium thin film prepared by the above method is a copper-vanadium-sulfur-selenium light-absorbing thin film.

[0024] The third objective of this invention is achieved by the following technical solution:

[0025] The application of the aforementioned copper-vanadium-sulfur-selenium thin film in the fabrication of solar cells is as follows: The copper-vanadium-sulfur-selenium thin film is immersed in a 1.3% cadmium sulfide solution, and a CdS buffer layer is deposited by a chemical bath method. The thickness of the CdS buffer layer is 40-60 nm, preferably 50 nm. The copper-vanadium-sulfur-selenium thin film with the CdS buffer layer is then placed in a magnetron sputtering device, and the vacuum degree is adjusted to 3.0 × 10⁻⁶. -3 An i-ZnO window layer and an ITO window layer are sequentially deposited by vapor deposition. The thickness of the i-ZnO window layer is 70-90 nm, preferably 80 nm, and the thickness of the ITO window layer is 150-250 nm, preferably 200 nm. The copper vanadium sulfur selenide thin film with the window layer prepared is then used to prepare an electrode by vacuum thermal evaporation. The electrode is an Al electrode or an Ag electrode, and the thickness of the electrode is 500-700 nm, preferably 600 nm. A copper vanadium sulfur selenide solar cell is thus obtained.

[0026] Advantages of this invention:

[0027] This invention addresses the problems of small grain size and insufficient density in existing copper-vanadium-sulfur-selenium (CPSS) light-absorbing films by proposing a method for preparing CPSS films based on an amine-thiol solution method, through optimized selenization conditions and doping with metal cations. Optimized selenization conditions result in CPSS films with larger grain sizes and reduced surface porosity, significantly improving film quality. Doping with metal cations such as sodium, bismuth, and cadmium ions promotes grain growth, increasing grain size and / or reducing film porosity, thus improving battery conversion efficiency. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 (a) SEM image of the copper vanadium sulfur thin film prepared in Comparative Example 1, (b) SEM image of the thin film interface, (c) grain size image, and (d) XRD pattern.

[0030] Figure 2 The JV curve is for the assembled solar cell of Comparative Example 1.

[0031] Figure 3 (a) SEM image of the copper vanadium sulfur thin film prepared in Comparative Example 2, (b) SEM image of the thin film interface, (c) grain size diagram, and (d) XRD pattern.

[0032] Figure 4 The JV curve is for the assembled solar cell of Comparative Example 2.

[0033] Figure 5 The images shown are: (a) SEM image of the film surface, (b) SEM image of the film interface, (c) grain size image, and (d) XRD pattern of the copper vanadium sulfur thin film prepared in Example 1.

[0034] Figure 6 This is a JV curve diagram of the assembled solar cell in Example 1;

[0035] Figure 7 The images shown are: (a) SEM image of the film surface, (b) SEM image of the film interface, (c) grain size image, and (d) XRD pattern of the copper vanadium sulfur thin film prepared in Example 2.

[0036] Figure 8The JV curve is shown for the assembled solar cell of Example 2;

[0037] Figure 9 The images shown are: (a) SEM image of the film surface, (b) SEM image of the film interface, (c) grain size image, and (d) XRD pattern of the copper vanadium sulfur thin film prepared in Example 3.

[0038] Figure 10 The JV curve is shown for the assembled solar cell of Example 3;

[0039] Figure 11 The images shown are: (a) SEM image of the film surface, (b) SEM image of the film interface, (c) grain size image, and (d) XRD pattern of the copper vanadium sulfur thin film prepared in Example 4.

[0040] Figure 12 The JV curve is shown for the assembled solar cell of Example 4;

[0041] Figure 13 The images shown are: (a) SEM image of the copper vanadium sulfur thin film prepared in Example 5; (b) SEM image of the thin film interface; (c) grain size diagram; and (d) XRD pattern.

[0042] Figure 14 The JV curve is shown for the assembled solar cell of Example 5;

[0043] Figure 15 The images shown are: (a) SEM image of the film surface, (b) SEM image of the film interface, (c) grain size image, and (d) XRD pattern of the copper vanadium sulfur thin film prepared in Example 6.

[0044] Figure 16 The image shows the JV curve of the assembled solar cell in Example 6. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Comparative Example 1

[0047] 2 mL of mercaptoacetic acid and 3 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 557.8 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred at 70 °C for another 30 min until the drug powder was completely dissolved. Next, 300 mg of selenium powder was added, and the mixture was magnetically stirred at 70 °C for another 30 min. Then, 301.4 mg of thiourea and 7 mL of ethylene glycol methyl ether were added, and the mixture was magnetically stirred at 70 °C for 30 min. After that, the mixture was centrifuged at 3000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide selenium (CVSSe) precursor solution free of impurities. The precursor solution was spin-coated on a spin coater and sintered at 320 °C for 1.5 min on a sintering stage. The spin-coating-sintering steps were repeated 8 times to obtain a copper vanadium sulfide selenium film. 350 mg of selenium powder was placed in a graphite box, and the selenization conditions were set at 510°C and 20 min under a nitrogen atmosphere to selenize the copper vanadium sulfur film to obtain a copper vanadium sulfur selenide (CVSSe) film. Figure 1 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared by the above steps is about 0.27 μm.

[0048] A copper-vanadium-sulfur-selenium (CVSGS) solar cell was prepared by depositing a 50 nm thick CdS buffer layer using a chemical bath method, followed by the deposition of an 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using a vacuum thermal evaporation method. Figure 2 As shown, the photoelectric conversion efficiency of the prepared solar cell is 4.99%.

[0049] Comparative Example 2

[0050] 1 mL of mercaptoacetic acid and 2 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 559 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred again at 100 °C for 30 min until all the drug powders were dissolved. The mixture was then cooled to room temperature, and 301.4 mg of thiourea and 5 mL of ethylene glycol methyl ether were added. The mixture was magnetically stirred at 25 °C for 60 min. Afterward, the mixture was centrifuged at 12000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide (CVS) precursor solution free of impurities. The precursor solution was spin-coated on a spin coater and sintered at 300 °C for 2 min on a sintering stage. This spin-coating-sintering step was repeated 7 times to obtain a copper vanadium sulfide (CVS) film. 400 mg of selenium granules were placed in a graphite box, and the selenization conditions were set at 500 °C for 70 min under a nitrogen atmosphere to selenize the copper vanadium sulfide film, obtaining a copper vanadium sulfide selenide (CVSSe) film with large grains. Figure 3 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared by the above steps is about 0.5 μm.

[0051] A copper-vanadium-sulfur-selenium (CVSGS) solar cell was prepared by depositing a 50 nm thick CdS buffer layer using a chemical bath method, followed by the deposition of an 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using a vacuum thermal evaporation method. Figure 4 As shown, the photoelectric conversion efficiency of the prepared solar cell is 3.76%.

[0052] Example 1

[0053] The overall composition is the same as Comparative Example 2, except that thiourea and ethylene glycol methyl ether were added to the solution and then magnetically stirred at 15°C for 60 min. Figure 5 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing thin film prepared in this embodiment is about 0.3 μm.

[0054] like Figure 6 As shown, the photoelectric conversion efficiency of the solar cell prepared from the above copper vanadium sulfur selenide light-absorbing thin film is 4.7%.

[0055] Example 2

[0056] The overall composition is the same as Comparative Example 2, except that thiourea and ethylene glycol methyl ether were added to the solution and then the mixture was magnetically stirred at 0°C for 60 min. Figure 7 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared in this embodiment is about 0.32 μm.

[0057] like Figure 8 As shown, the photoelectric conversion efficiency of the solar cell prepared from the above-mentioned copper vanadium sulfur selenide light-absorbing thin film is 5.08%. As seen in Examples 1 and 2, higher stirring temperatures cause oxidation of the CVS precursor solution, resulting in impurities. During high-temperature selenization, the decomposition and evaporation of these impurities at high temperatures leads to pores in the film. Therefore, lower stirring temperatures can prevent oxidation of the CVS precursor solution and the generation of impurities, which is beneficial for enhancing the film's density and improving the photoelectric conversion efficiency of the solar cell prepared from the film.

[0058] Example 3

[0059] 1 mL of mercaptoacetic acid and 2 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 559 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred at 100 °C for another 30 min until the drug powder was completely dissolved. The mixture was then cooled to room temperature, and 301.4 mg of thiourea and 5 mL of ethylene glycol methyl ether were added. The mixture was magnetically stirred at 0 °C for 60 min. Afterward, the mixture was centrifuged at 12000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide (CVS) precursor solution free of impurities. The precursor solution was spin-coated onto molybdenum glass and sintered at 300 °C for 2 min on a sintering stage. The spin-coating-sintering step was repeated 7 times to obtain a copper vanadium sulfide (CVS) film. 400 mg of selenium granules were placed in a graphite box, and a 1 mm thick layer of soda-lime glass was placed on a pre-fabricated copper vanadium sulfur film. Selenization was carried out under a nitrogen atmosphere at 530 °C for 70 min to obtain a copper vanadium sulfur selenide (CVSSe) film. Figure 9 As shown, the grain size of the copper-vanadium-sulfur-selenium light-absorbing thin film prepared in the above steps is approximately 0.36 μm. Figure 9 (a) and Figure 7 (a) As can be seen from the comparison, the film in this embodiment has stronger compactness.

[0060] A copper-vanadium-sulfur-selenium (CVSGS) solar cell was prepared by depositing a 50 nm thick CdS buffer layer using a chemical bath method, followed by the deposition of an 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using a vacuum thermal evaporation method. Figure 10 As shown, the photoelectric conversion efficiency of the prepared solar cell is 5.53%. This embodiment optimizes the selenization conditions compared to Example 2, which is beneficial to further improve the photoelectric conversion efficiency.

[0061] Example 4

[0062] 1 mL of mercaptoacetic acid and 2 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 559 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred at 100 °C for another 30 min until the drug powder was completely dissolved. The mixture was then cooled to room temperature, and 301.4 mg of thiourea, 0.5% sodium acetate (sodium ion molar percentage in the solution was 0.5%), and 5 mL of ethylene glycol methyl ether were added. The mixture was magnetically stirred at 0 °C for 60 min. Afterward, the mixture was centrifuged at 12000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide (CVS) precursor solution. The precursor solution was spin-coated on a spin coater and sintered at 300 °C for 2 min on a sintering stage. The spin-coating-sintering step was repeated 7 times to obtain a copper vanadium sulfide (CVS) film. 400 mg of selenium granules were placed in a graphite box, and the selenization conditions were set at 500℃ for 70 min under a nitrogen atmosphere to selenize a copper vanadium sulfide thin film, resulting in a sodium-doped copper vanadium sulfide selenide (CVSSe) thin film with large grains. Figure 11 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared by the above steps is about 0.38 μm.

[0063] A 50 nm thick CdS buffer layer was deposited in a copper-vanadium-sulfur-selenium (Cvanadium-sulfur-selenium) thin film using a chemical bath deposition method. An 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer were then deposited using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using vacuum thermal evaporation to obtain a 0.5% sodium-doped Cvanadium-sulfur-selenium solar cell. Figure 12 As shown, the photoelectric conversion efficiency of the prepared solar cell is 5.87%. It can be seen that doping with sodium ions can promote grain growth, reduce thin film pores, and improve photoelectric conversion efficiency.

[0064] Example 5

[0065] 1 mL of mercaptoacetic acid and 2 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 559 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred at 100 °C for another 30 min until all the drug powders were dissolved. The mixture was then cooled to room temperature, and 301.4 mg of thiourea, 1% bismuth nitrate (1% molar percentage of bismuth ions in the solution), and 5 mL of ethylene glycol methyl ether were added. The mixture was magnetically stirred at 0 °C for 60 min. Afterward, the mixture was centrifuged at 12000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide (CVS) precursor solution with 1% bismuth doping. The precursor solution was spin-coated on a spin coater and sintered at 300 °C for 2 min on a sintering stage. The spin-coating-sintering step was repeated 7 times to obtain a copper vanadium sulfide (CVS) film. 400 mg of selenium granules were placed in a graphite box, and the selenization conditions were set at 500 °C for 70 min under a nitrogen atmosphere to selenize a copper vanadium sulfide thin film, resulting in a copper vanadium sulfide selenide (CVSSe) thin film doped with bismuth ions and possessing large grains. Figure 13 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared by the above steps is about 0.44 μm.

[0066] A 50 nm thick CdS buffer layer was deposited using a chemical bath method, followed by an 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer deposited using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using a vacuum thermal evaporation method to obtain a 1% bismuth-doped copper vanadium sulfur selenide solar cell. Figure 14 As shown, the photoelectric conversion efficiency of the prepared solar cell is 3.28%. It can be seen that bismuth doping can significantly promote grain growth, but it is lacking in terms of thin film density and photoelectric conversion capability.

[0067] Example 6

[0068] 1 mL of mercaptoacetic acid and 2 mL of ethanolamine were added to an Erlenmeyer flask and magnetically stirred at 70 °C for 30 min. Then, 559 mg of copper acetate and 259.8 mg of acetylacetone vanadium oxide were added, and the mixture was magnetically stirred at 100 °C for another 30 min until all the drug powders were dissolved. The mixture was then cooled to room temperature, and 301.4 mg of thiourea, 0.5% cadmium sulfate 3 / 8 hydrate (cadmium ion molar percentage in the solution was 0.5%), and 5 mL of ethylene glycol methyl ether were added. The mixture was magnetically stirred at 0 °C for 60 min. Afterward, the mixture was centrifuged at 12000 r / min for 5 min to obtain a homogeneous copper vanadium sulfide (CVS) precursor solution. The precursor solution was spin-coated on a spin coater and sintered at 300 °C for 2 min on a sintering stage. The spin-coating-sintering step was repeated 7 times to obtain a copper vanadium sulfide (CVS) film. 400 mg of selenium granules were placed in a graphite box, and a 1 mm thick layer of soda-lime glass was applied to a pre-fabricated copper vanadium sulfide (CVSSe) thin film. The CVSSe film was selenized under nitrogen atmosphere at 530 °C for 70 min to obtain a cadmium-doped CVSSe thin film with large grains. Figure 15 As shown, the grain size of the copper vanadium sulfur selenide light-absorbing film prepared by the above steps is about 0.40 μm. It can be seen that doping with cadmium ions can promote grain growth and reduce film pores, effectively improving the film density.

[0069] A 50 nm thick CdS buffer layer was deposited in a copper-vanadium-sulfur-selenium (Cvanadium-sulfur-selenium) thin film using a chemical bath deposition method. An 80 nm thick i-ZnO layer and a 200 nm thick ITO window layer were then deposited using magnetron sputtering. Finally, a 600 nm thick Al electrode was fabricated using vacuum thermal evaporation to obtain a 0.5% sodium-doped Cvanadium-sulfur-selenium solar cell. Figure 16 As shown, the photoelectric conversion efficiency of the prepared solar cell is 6.18%. The doping of Cd allows some Cd to enter the interior of the grain and replace some Cu, increasing the number of Cu vacancies in the crystal, increasing the effective hole concentration in the thin film, reducing the resistivity of the thin film, and significantly improving the efficiency of the copper vanadium sulfur selenide thin film device, thus enhancing the photoelectric conversion efficiency.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a copper-vanadium-sulfur-selenium light-absorbing thin film, comprising steps S1 and S2; wherein step S1: mercaptoacetic acid and ethanolamine are added to a reaction vessel, and the mixture is stirred to obtain a molecular solution, the reaction temperature is 60-100℃, and the reaction time is 10-60 min; step S2: a copper source and a vanadium source are added to the molecular solution, and the mixture is reacted until the copper source and the vanadium source are completely dissolved, the reaction temperature is 60-100℃, and the reaction time is 10-60 min, to obtain a mixed solution; Its features are, It also includes: Step S3: Add a sulfur source and a metal cation to the mixed solution, and add ethylene glycol methyl ether. React until the sulfur source is completely dissolved to obtain a copper-vanadium-sulfur precursor solution. The reaction temperature is 0~20℃ and the time is 30~120 min. The volume ratio of the ethylene glycol methyl ether to the mercaptoacetic acid and the ethanolamine is (3~7):(1~3):(1~4). The molar ratio of the metal cation doping is ≤1%. The metal cation includes at least one of sodium ion, cadmium ion, and bismuth ion. Step S4: Spin-coat and sinter the copper vanadium sulfur precursor solution to obtain a copper vanadium sulfur film; the sintering temperature is 300~320℃, the time is 1.5~6 min, and the spin-coating and sintering process is repeated 4~10 times; Step S5: Add the copper vanadium sulfur thin film obtained in S4 to a selenium source and carry out a selenization reaction to obtain a copper vanadium sulfur selenium thin film with large grains of doped metal cations; the selenization temperature of the selenization reaction is 350~560℃ and the reaction time is 10~90 min.

2. A method for preparing a copper-vanadium-sulfur-selenium light-absorbing thin film, comprising steps P1 and P2; wherein step P1: mercaptoacetic acid and ethanolamine are added to a reaction vessel, and the mixture is stirred to obtain a molecular solution, the reaction temperature is 60~100℃, and the time is 10~60 min; wherein step P2: a copper source and a vanadium source are added to the molecular solution, and the mixture is reacted until the copper source and the vanadium source are completely dissolved, the reaction temperature is 60~100℃, and the time is 10~60 min, to obtain a mixed solution; Its features are, It also includes: Step P3: Add a sulfur source, a metal cation, and ethylene glycol methyl ether to the mixed solution. React until the sulfur source is completely dissolved to obtain a copper-vanadium-sulfur precursor solution. The reaction temperature is 0-20℃ and the time is 30-120 min. The volume ratio of ethylene glycol methyl ether to mercaptoacetic acid and ethanolamine is (3-7):(1-3):(1-4). The molar ratio of the metal cation is ≤1%. The metal cation includes at least one of sodium ion, cadmium ion, and bismuth ion. Step P4: Spin-coat and sinter the copper vanadium sulfur precursor solution to obtain a copper vanadium sulfur film; the sintering temperature is 300~320℃, the time is 1.5~6 min, and the spin-coating and sintering process is repeated 4~10 times; Step P5: Add the copper vanadium sulfur thin film obtained in P4 to a selenium source, and cover the copper vanadium sulfur thin film with a layer of soda-lime glass. After the selenization reaction, a copper vanadium sulfur selenium thin film with large grains of doped metal cations is obtained. The selenization temperature of the selenization reaction is 510~550℃ and the reaction time is 10~90 min.

3. The copper-vanadium-sulfur-selenium thin film prepared by the method of claim 1 or 2.

4. The application of the copper-vanadium-sulfur-selenium thin film according to claim 3 in the preparation of solar cells, characterized in that, The copper-vanadium-sulfur-selenium thin film of claim 3 is immersed in a 1.3% cadmium sulfide solution, and a CdS buffer layer with a thickness of 40-60 nm is deposited by a chemical bath method; the copper-vanadium-sulfur-selenium thin film with the CdS buffer layer is then placed in a magnetron sputtering device, and the vacuum degree is adjusted to 3.0 × 10⁻⁶. -3 An i-ZnO window layer and an ITO window layer are sequentially deposited by vapor deposition. The thickness of the i-ZnO window layer is 70-90 nm, and the thickness of the ITO window layer is 150-250 nm. The copper vanadium sulfur selenide thin film with the window layer prepared is then used to prepare an electrode by vacuum thermal evaporation. The electrode is an Al electrode or an Ag electrode, and the thickness of the electrode is 500-700 nm. A copper vanadium sulfur selenide solar cell is thus obtained.

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