A ternary metal sulfide nanocrystal thin film, a preparation method and application thereof

Abstract

This invention belongs to the field of semiconductor nanofilm technology, specifically relating to a ternary metal sulfide nanocrystalline thin film, its preparation method, and its applications. Based on a low-temperature solution process, this invention innovatively employs a two-step method to prepare ternary metal sulfide nanocrystalline thin films in situ on a substrate. First, a molecular precursor is prepared by dissolving a metal salt using a short-chain organic amine as a solvent. The soft template effect of the organic linear amine is then used to prepare a porous cationic thin film on the substrate. Subsequently, a sulfur source precursor solution is prepared by dissolving a sulfur source in acetone, an orthogonal solvent that does not damage the cationic thin film. This solution is then used to treat the cationic thin film multiple times before low-temperature annealing to form the ternary metal sulfide nanocrystalline thin film. The prepared film exhibits high-purity phase, standard stoichiometry, and excellent light absorption performance. The film surface shows no obvious agglomeration and exhibits good flatness and density. It has great application potential as an absorption layer for various optoelectronic devices.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor nanofilm technology, specifically relating to a ternary metal sulfide nanocrystalline thin film, its preparation method, and its application. Background Technology

[0002] Ternary metal sulfide nanocrystals (such as AgBiS2, AgInS2, Cu3BiS3, CuInS2, etc.) possess tunable band structures (1.0~2.0 eV) and high light absorption coefficients (>10 eV) due to their size and composition dependence. 5 cm -1 With its environmentally friendly properties (low toxicity, high element abundance), it has become a key functional material for the next generation of optoelectronic devices, and is mainly used in solar cells (such as quantum dot sensitized / heterojunction solar cells), photodetectors (broad spectral response, covering the visible to near-infrared band), solar fluorescent concentrators (tunable fluorescence emission characteristics, improving solar cell performance) and photocatalysis (such as solar fuel preparation and pollutant degradation).

[0003] The solution preparation of such chalcogenide nanocrystalline films mainly includes the following methods: (1) Hot Injection: Metal precursors (such as acetates, acetylacetone compounds) and sulfur sources (such as thiourea, sulfur powder, dodecanethiol) are rapidly mixed in a high-temperature organic solvent (such as oleylamine, octadecene) to form nanocrystals with controllable morphology and excellent monodispersity. The obtained nanocrystals must be cleaned and purified to remove unreacted precursors, and then redispersed in a nonpolar solvent to form a colloidal solution, and then formed into a film by spin coating, drop coating or blade coating. However, in the later optoelectronic applications, the surface coating of insulating ligands requires repeated ligand exchange processes, resulting in uncontrollable film morphology, which directly affects the optoelectronic performance of the later film. (2) Molecular Precursor Solution Method: Metal salts (such as nitrates, chlorides) and sulfur sources (such as thiourea) are dissolved in a solvent (such as DMF, ethylene glycol), and then formed into a film by spin coating or spray coating and annealing. This process is suitable for large-area preparation, but may leave organic impurities, and the reaction rate is uncontrollable. The grain size is prone to excessive growth, leading to non-uniformity and coarsening. (3) Solvothermal / Hydrothermal method: The reaction is carried out in a closed reactor under high temperature and high pressure. Thin films can be directly epitaxially grown on the substrate or formed into films after synthesizing nanocrystals. The thin films prepared by this process have good crystallinity, but the equipment requirements are high. (4) Ion exchange method: First, a nanocrystal (such as Cu2S) is synthesized, and then ion exchange (such as Ag) is performed. + Replace Cu + It can be transformed into the target material (such as AgBiS2). The composition can be controlled, but the reaction kinetics are complex. Summary of the Invention

[0004] The purpose of this invention is to provide a ternary metal sulfide nanocrystalline thin film, its preparation method, and its application. The nanocrystalline thin film obtained by the method provided by this invention has no obvious particle agglomeration, is flat and dense, and has high phase purity close to the standard stoichiometry and good light absorption characteristics, making it suitable for use as a light absorption layer in various optoelectronic devices.

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

[0006] This invention provides a method for preparing ternary metal sulfide nanocrystalline thin films, comprising the following steps:

[0007] A first metal salt, a second metal salt, and a short-chain organic amine are mixed to obtain a metal salt precursor solution; the first metal salt is a transition metal salt, and the second metal salt is at least one of a Group IIIA metal salt and a Group VA metal salt;

[0008] The metal salt precursor solution is first coated on the substrate surface to obtain a cationic precursor film.

[0009] After the anionic reaction precursor solution is coated a second time onto the cationic precursor film, it is annealed to obtain the ternary metal sulfide nanocrystalline film; the components of the anionic reaction precursor solution are sulfur source and acetone.

[0010] Preferably, the transition metal salt includes at least one of silver salt and copper salt;

[0011] The group IIIA metal salts include at least one of indium salts and gallium salts;

[0012] The Group VA metal salts include bismuth salts.

[0013] Preferably, the short linear organic amine includes at least one of n-butylamine, n-pentylamine, and n-hexylamine.

[0014] Preferably, the molar ratio of the first metal salt to the second metal salt is 1:1 to 1.3;

[0015] The ratio of the first metal salt to the short-chain organic amine is 0.25~0.40 mmol: 1.00 mL;

[0016] The mixing is performed under ultrasonic conditions;

[0017] The first coating method is spin coating, the spin coating speed is 2000~4000 rpm, and the time is 20~40s; the mixing and the first coating are both carried out under a protective atmosphere.

[0018] Preferably, the sulfur source includes at least one of thiourea and N,N-diphenylthiourea.

[0019] Preferably, the ratio of sulfur source to acetone is 0.5~0.8 mmol: 1 mL;

[0020] The preparation of the anion reaction precursor solution includes: ultrasonically mixing and centrifuging a sulfur source and acetone sequentially; the ultrasonic mixing time is 30-60 min, and the centrifugation speed is 3500-5000 rpm for 5-10 min.

[0021] Preferably, the molar ratio of the first metal salt to the sulfur source is 1:2~5;

[0022] The second coating method is spin coating, wherein the spin coating speed is 2000~4000 rpm and the time is 20~40s.

[0023] Preferably, the annealing temperature is 120~160℃ and the time is 15~30min;

[0024] The relative humidity for both the second coating and annealing is below 10%.

[0025] The present invention also provides a ternary metal sulfide nanocrystalline thin film prepared by the preparation method described in the above technical solution.

[0026] The present invention also provides the application of the ternary metal sulfide nanocrystalline thin film described above in solar cells, photodetectors, solar fluorescent concentrators, or photocatalysis.

[0027] This invention, based on a low-temperature solution process, innovatively employs a two-step method to prepare ternary metal sulfide nanocrystalline films in situ on a substrate. First, a molecular precursor is prepared by dissolving a metal salt using a short-chain organic amine as a solvent. The soft template effect of the organic linear amine enables the fabrication of a porous cationic film on the substrate. Subsequently, a sulfur source precursor solution is prepared by dissolving a sulfur source in acetone, an orthogonal solvent that does not damage the cationic film. This solution is then used to treat the cationic film multiple times, followed by low-temperature annealing to form the ternary metal sulfide nanocrystalline film. The prepared film exhibits high-purity phase, standard stoichiometry, and excellent light absorption performance. The film surface shows no obvious agglomeration and exhibits good flatness and density. It has enormous application potential as an absorption layer for various optoelectronic devices. Attached Figure Description

[0028] Figure 1 SEM images of the cationic precursor films obtained in Examples 1-4;

[0029] Figure 2 SEM images of the nanocrystalline thin films obtained in Examples 1-4;

[0030] Figure 3The XRD patterns are of the nanocrystalline thin films obtained in Examples 1-4;

[0031] Figure 4 The EDS energy spectrum and atomic percentage of the nanocrystalline thin films obtained in Examples 1-4 are shown.

[0032] Figure 5 The UV-Vis absorption spectra of the nanocrystalline thin films obtained in Examples 1-4 are shown.

[0033] Figure 6 The figure shows the current-ampere (JV) characteristic curve of the solar cell obtained in the application example. Detailed Implementation

[0034] This invention provides a method for preparing ternary metal sulfide nanocrystalline thin films, comprising the following steps:

[0035] A first metal salt, a second metal salt, and a short-chain organic amine are mixed to obtain a metal salt precursor solution; the first metal salt is a transition metal salt, and the second metal salt is at least one of a Group IIIA metal salt and a Group VA metal salt;

[0036] The metal salt precursor solution is first coated on the substrate surface to obtain a cationic precursor film.

[0037] After the anionic reaction precursor solution is coated a second time onto the cationic precursor film, it is annealed to obtain the ternary metal sulfide nanocrystalline film; the components of the anionic reaction precursor solution are sulfur source and acetone.

[0038] The present invention mixes a first metal salt, a second metal salt and a short linear organic amine to obtain a metal salt precursor solution; the first metal salt is a transition metal salt, and the second metal salt is at least one of a group IIIA metal salt and a group VA metal salt.

[0039] In this invention, the transition metal salt preferably includes at least one of silver salt and copper salt; the silver salt preferably includes at least one of Ag(CH3COO) and AgNO3; and the copper salt preferably includes at least one of Cu(CH3COO)2 and Cu(NO3).

[0040] In this invention, the Group IIIA metal salt preferably includes at least one of indium and gallium; the indium salt preferably includes at least one of In(CH3COO)3 and In(NO3)3; the gallium salt preferably includes at least one of Ga(CH3COO)3 and Ga(NO3)3. In this invention, the Group VA metal salt preferably includes a bismuth salt; the bismuth salt preferably includes at least one of Bi(CH3COO)3 and Bi(NO3)3.

[0041] In this invention, the short linear organic amine preferably includes at least one of n-butylamine, n-pentylamine, and n-hexylamine.

[0042] In this invention, the molar ratio of the first metal salt to the second metal salt is preferably 1:1 to 1.3, specifically 1:1, 1:1.1, 1:1.2, or 1:1.3; the molar ratio of the first metal salt to the short-chain organic amine is preferably 0.25 to 0.40 mmol: 1.00 mL, specifically 0.25 mmol: 1 mL, 0.3 mmol: 1.00 mL, or 0.40 mmol: 1.00 mL; the mixing is preferably performed under ultrasonic conditions; the ultrasonic time is preferably 60 min; the mixing is preferably performed under a protective atmosphere, preferably including nitrogen or argon.

[0043] After obtaining the metal salt precursor solution, the present invention performs a first coating on the substrate surface to obtain a cationic precursor film.

[0044] In this invention, the substrate preferably includes an ITO substrate. In this invention, prior to the first coating, it is also preferable to pretreat the substrate, the pretreatment preferably including: ultrasonic cleaning with acetone, isopropanol, and deionized water sequentially for 15 minutes, followed by drying with N2, and then treatment in a UV-O3 environment for 30 minutes.

[0045] In this invention, the first coating method is preferably spin coating, and the spin coating speed is preferably 2000~4000 rpm, specifically 2000 rpm, 3000 rpm, or 4000 rpm; the time is preferably 20~40 s, specifically 20 s, 30 s, or 40 s; after spin coating, it is also preferable to dry the obtained wet film, and the drying temperature is preferably 110°C, and the drying time is preferably 15 min. In this invention, the first coating is preferably carried out under a protective atmosphere, and the protective atmosphere preferably includes nitrogen or argon.

[0046] After obtaining the cationic precursor film, the present invention performs a second coating of the anionic reaction precursor liquid on the cationic precursor film and then anneals it to obtain the ternary metal sulfide nanocrystalline film; the anionic reaction precursor liquid includes a sulfur source and acetone.

[0047] In this invention, the anion reaction precursor solution comprises a sulfur source and acetone. Preferably, the sulfur source comprises at least one of thiourea and N,N-diphenylthiourea; the ratio of sulfur source to acetone is preferably 0.5-0.8 mmol:1 mL, specifically 0.5 mmol:1 mL, 0.6 mmol:1 mL, 0.7 mmol:1 mL, or 0.8 mmol:1 mL.

[0048] In this invention, the preparation of the anionic reaction precursor solution preferably includes: sequentially ultrasonically mixing and centrifuging a sulfur source and acetone; the ultrasonic mixing time is preferably 30 min, the centrifugation speed is preferably 5000 rpm, and the centrifugation time is preferably 5 min; the ultrasonic mixing is preferably carried out in an acrylic glove box, and the relative humidity in the acrylic glove box is preferably below 10%, specifically 3%, 5%, or 10%. In this invention, acetone has very weak polarity; although it can dissolve the sulfur source, it will not damage the pre-deposited metal salt precursor film, thus ensuring the subsequent reaction between the metal salt precursor film and the sulfur source.

[0049] In this invention, the molar ratio of the first metal salt to the sulfur source is preferably 1:2 to 5, specifically 1:2, 1:3, 1:4, or 1:5; the second coating method is preferably spin coating, and the spin coating speed is preferably 2000 to 4000 rpm, specifically 2000 rpm, 3000 rpm, or 4000 rpm; the time is preferably 20 to 40 seconds, specifically 20 seconds, 30 seconds, or 40 seconds. In this invention, the second coating is preferably carried out in an acrylic glove box, and the relative humidity in the acrylic glove box is preferably below 10%, specifically 3%, 5%, or 10%.

[0050] In this invention, the annealing temperature is preferably 120~160℃, specifically 120℃, 130℃, 140℃, 150℃, or 160℃, and the annealing time is preferably 15~30 min, specifically 15 min, 20 min, 25 min, or 30 min. After annealing, it is also preferable to cool the obtained film to room temperature. In this invention, the annealing is preferably carried out in an acrylic glove box, and the relative humidity in the acrylic glove box is preferably below 10%, specifically 3%, 5%, or 10%. In this invention, annealing enables better crystallization of the film to obtain the target product, and by controlling the relative humidity, oxidation can be prevented, further improving the crystallization performance.

[0051] The present invention also provides a ternary metal sulfide nanocrystalline thin film prepared by the preparation method described in the above technical solution.

[0052] The present invention also provides the application of the ternary metal sulfide nanocrystalline thin film described above in solar cells, photodetectors, solar fluorescent concentrators, or photocatalysis.

[0053] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0054] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0055] Example 1

[0056] The ITO substrate was ultrasonically cleaned with acetone, isopropanol and deionized water for 15 min in sequence, dried with N2, and then placed in a UV-O3 environment for 30 min for pretreatment.

[0057] Under a nitrogen atmosphere, 0.25 mmol Ag(CH3COO) and 0.25 mmol Bi(CH3COO)3 were dissolved in 1 mL n-butylamine and treated with an ultrasonic cell disruptor for 60 min to obtain an Ag / Bi cation reaction precursor solution. The solution was spin-coated onto a pretreated ITO substrate at 2000 rpm for 30 s and dried at 110 °C for 15 min to form a cation precursor film.

[0058] In an acrylic glove box (with relative humidity controlled at 5%), 0.5 mmol of thiourea was dissolved in 1 mL of acetone and treated with an ultrasonic cell disruptor for 30 min. The mixture was then centrifuged at 5000 rpm for 5 min to obtain a clear anionic reaction precursor solution. 200 μL of the anionic reaction precursor solution was spin-coated onto a cationic precursor film at 2000 rpm for 30 s. The ITO substrate was then placed on a heating platform for annealing at 150 °C for 15 min. After the ITO substrate cooled down, AgBiS2 nanocrystalline films were obtained.

[0059] Example 2

[0060] The ITO substrate was ultrasonically cleaned with acetone, isopropanol and deionized water for 15 min in sequence, dried with N2, and then placed in a UV-O3 environment for 30 min for pretreatment.

[0061] Under a nitrogen atmosphere, 0.25 mmol Ag(CH3COO) and 0.25 mmol In(CH3COO)3 were dissolved in 1 mL n-butylamine and treated with an ultrasonic cell disruptor for 60 min to obtain an Ag / In cation reaction precursor solution. The solution was spin-coated onto a pretreated ITO substrate at 2000 rpm for 30 s and dried at 110 °C for 15 min to form a cation precursor film.

[0062] In an acrylic glove box (with relative humidity controlled at 3%), 0.5 mmol of thiourea was dissolved in 1 mL of acetone and treated with an ultrasonic cell disruptor for 30 min. The mixture was then centrifuged at 5000 rpm for 5 min to obtain a clear anionic reaction precursor solution. 200 μL of the anionic reaction precursor solution was spin-coated onto a cationic precursor film at 2000 rpm for 30 s. The ITO substrate was then placed on a heating platform for annealing at 150 °C for 15 min. After the ITO substrate cooled down, AgInS2 nanocrystalline films were obtained.

[0063] Example 3

[0064] The ITO substrate was ultrasonically cleaned with acetone, isopropanol and deionized water for 15 min in sequence, dried with N2, and then placed in a UV-O3 environment for 30 min for pretreatment.

[0065] Under a nitrogen atmosphere, 0.25 mmol Cu(CH3COO) and 0.25 mmol Bi(CH3COO)3 were dissolved in 1 mL n-butylamine and treated with an ultrasonic cell disruptor for 60 min to obtain a Cu / Bi cation reaction precursor solution. The solution was spin-coated onto a pretreated ITO substrate at 2000 rpm for 30 s and dried at 110 °C for 15 min to form a cation precursor film.

[0066] In an acrylic glove box (with relative humidity controlled at 10%), 0.5 mmol of thiourea was dissolved in 1 mL of acetone and treated with an ultrasonic cell disruptor for 30 min. The mixture was then centrifuged at 5000 rpm for 5 min to obtain a clear anionic reaction precursor solution. 200 μL of the anionic reaction precursor solution was spin-coated onto a cationic precursor film at 2000 rpm for 30 s. The ITO substrate was then placed on a heating platform for annealing at 150 °C for 15 min. After the ITO substrate cooled down, a Cu3BiS3 nanocrystalline film was obtained.

[0067] Example 4

[0068] The ITO substrate was ultrasonically cleaned with acetone, isopropanol and deionized water for 15 min in sequence, dried with N2, and then placed in a UV-O3 environment for 30 min for pretreatment.

[0069] Under a nitrogen atmosphere, 0.25 mmol Cu(CH3COO) and 0.25 mmol In(CH3COO)3 were dissolved in 1 mL n-butylamine and treated with an ultrasonic cell disruptor for 60 min to obtain a Cu / In cation reaction precursor solution. The solution was spin-coated onto a pretreated ITO substrate at 2000 rpm for 30 s and dried at 110 °C for 15 min to form a cation precursor film.

[0070] In an acrylic glove box (with relative humidity controlled at 5%), 0.5 mmol of thiourea was dissolved in 1 mL of acetone and treated with an ultrasonic cell disruptor for 30 min. The mixture was then centrifuged at 5000 rpm for 5 min to obtain a clear anionic reaction precursor solution. 200 μL of the anionic reaction precursor solution was spin-coated onto a cationic precursor film at 2000 rpm for 30 s. The ITO substrate was then placed on a heating platform for annealing at 150 °C for 15 min. After the ITO substrate cooled down, a CuInS2 nanocrystalline film was obtained.

[0071] Performance testing

[0072] Test Example 1

[0073] Figure 1 SEM images of the cationic precursor films obtained in Examples 1-4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4;

[0074] As can be seen, the cationic precursor films all exhibit a porous morphology, which provides a channel for the subsequent full penetration reaction of the anionic precursor. The formation of the above morphology is mainly due to the soft film effect of the linear structure of n-butylamine.

[0075] Test Example 2

[0076] Figure 2 The images show SEM images of the nanocrystalline thin films obtained in Examples 1-4, where (a) is AgBiS2, (b) is AgInS2, (c) is Cu3BiS3, and (d) is CuInS2.

[0077] It can be seen that selecting acetone, an orthogonal solvent, as the carrier for thiourea can effectively avoid damage to the morphology of the cationic precursor film during the treatment process. Furthermore, its low specific surface tension allows for the induction of a full reaction between thiourea and the cationic precursor through the pore channels present in the cationic precursor film, forming a dense and flat ternary nanocrystalline film. Figure 2 As shown in (a,b,d), the Cu3BiS3 thin film exhibits relatively uniform "rice grain" shaped nanocrystals, which is mainly related to the unique crystallization form of Cu3BiS3.

[0078] Test Example 3

[0079] Figure 3 The images show the XRD patterns of the nanocrystalline thin films obtained in Examples 1-4, where (a) is AgBiS2, (b) is AgInS2, (c) is Cu3BiS3, and (d) is CuInS2.

[0080] It can be seen that the obtained films all correspond to their respective phases. After sulfurization, Ag / Bi cation films yield AgBiS2 nanocrystalline films, which correspond to standard card JCPDS 089-2045; after sulfurization, Ag / In cation films yield AgInS2 nanocrystalline films, which correspond to standard card JCPDS 025-1328; after sulfurization, Cu / Bi cation films yield Cu3BiS3 nanocrystalline films, which correspond to standard card JCPDS 043-1479; and after sulfurization, Cu / In cation films yield CuInS2 nanocrystalline films, which correspond to standard card JCPDS 047-1372.

[0081] Test Example 4

[0082] Figure 4 The EDS energy spectrum and atomic content percentage of the nanocrystalline thin films obtained in Examples 1-4 are shown, where (a) is AgBiS2, (b) is AgInS2, (c) is Cu3BiS3, and (d) is CuInS2.

[0083] The nanocrystalline thin films obtained above were subjected to quantitative compositional energy dispersive spectroscopy analysis, and the atomic percentages were respectively at... Figure 4 As given in (ad), the stoichiometric ratios of AgBiS2, AgInS2, Cu3BiS3, and CuInS2 can be calculated to be 1.15:1:2, 1.09:1:2, 3.10:1:3.00, and 1.00:1.10:2.00, respectively, which are very close to the standard stoichiometric ratios of their respective chemical formulas.

[0084] Test Example 5

[0085] Figure 5 The UV-vis absorption spectra of the nanocrystalline thin films obtained in Examples 1-4 are shown, where (a) is AgBiS2, (b) is AgInS2, (c) is Cu3BiS3, and (d) is CuInS2.

[0086] The obtained AgBiS2, Cu3BiS3, and CuInS2 films all exhibit good optical absorption coverage of the visible light region. In particular, AgBiS2 can extend into the near-infrared region comparable to Si, with an absorption cutoff edge of 1097 nm and a corresponding band gap of 1.13 eV; while AgInS2 film cannot completely cover the visible light region, with an absorption cutoff edge of 659 nm and a corresponding band gap of 1.88 eV.

[0087] Application examples

[0088] Solar cells were fabricated using FTO / ZnO / absorber / Spiro-OMeTAD / Au as the device structure. The fabrication process and JV testing procedure are as follows:

[0089] Preparation of colloidal ZnO nanocrystals: First, a 250 mL three-necked flask was placed in an oil bath, and 2.95 g of zinc acetate dihydrate and 125 mL of methanol were added sequentially. The mixture was heated to 60 °C and stirred. Then, 65 mL of potassium hydroxide solution (mKOH = 1.48 g) in methanol was slowly added over 20 minutes, and the reaction was continued for 2.5 hours after the addition was complete. The reaction solution was allowed to stand overnight in the dark, and the supernatant was discarded. The resulting ZnO nanocrystal precipitate was thoroughly mixed with 50 mL of methanol and washed twice: for the first wash, 50 mL of methanol was added and vortexed for 90 seconds, followed by centrifugation at 3500 rpm for 5 minutes; for the second wash, the mixture was vortexed for 90 seconds and centrifuged at 8000 rpm for 5 minutes. The final solid was dissolved in 4 mL of chloroform, and 16 mL of methanol was added to bring the volume to 20 mL, yielding a clear and transparent ZnO nanocrystal spin-coated solution.

[0090] Preparation of spin-coating solution for hole transport layer: First, weigh 72.3 mg of Spiro-OMeTAD powder and dissolve it in 1 mL of anhydrous chlorobenzene. Then, add 28 μL of tBP solution, 15 μL of FK209 / acetonitrile mixed solution (375 mg / mL), and 16 μL of LiTFSI / acetonitrile mixed solution (520 mg / mL) in sequence. Stir at room temperature for more than 3 hours to ensure complete dissolution.

[0091] Device fabrication: The etched FTO conductive glass was ultrasonically cleaned in a mild detergent solution for 30 minutes, rinsed three times with deionized water, and then ultrasonically treated in acetone, isopropanol, and deionized water for 15 minutes each. After drying, it underwent a 30-minute UV ozone activation treatment. Subsequently, a ZnO solution was spin-coated onto the FTO substrate at 4500 rpm for 25 seconds to form a film. Then, nanocrystalline thin films as absorption layers in Examples 1-4 were prepared on the FTO / ZnO substrate. Subsequently, 75-80 μL of Spiro-OMeTAD solution was uniformly dropped onto the surface of the absorption layer film at a speed of 1000 rpm for 5 seconds and 4000 rpm for 45 seconds to prepare a uniform hole transport layer. Then, approximately 80 nm of Au was thermally evaporated as an electrode to complete the entire device fabrication. After fabrication, the device was oxidized overnight in a drying oven with a relative humidity of less than 5% before JV testing.

[0092] JV test conditions: AM 1.5G spectrum, intensity: 100mW / cm² 2 The light-receiving surface of the device is controlled at 0.04 cm. 2 The scanning range is -0.1 to 0.6V, the scanning step value is 0.01V, and the scanning dwell time at each point is 100ms.

[0093] Figure 6The current-ampere (JV) characteristic curves of the obtained solar cells are shown, where (a) is AgBiS2, (b) is AgInS2, (c) is Cu3BiS3, and (d) is CuInS2.

[0094] As can be seen, the solar cell with AgBiS2 thin film as the absorber layer in Example 1 achieved a photoelectric conversion efficiency of 2.65%. The corresponding devices with AgInS2, Cu3BiS3 and CuInS2 thin films had efficiencies of 1.238%, 0.729% and 1.982%, respectively, exhibiting the expected photovoltaic characteristics.

[0095] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a ternary metal sulfide nanocrystalline thin film, characterized in that, The steps are as follows: The ternary metal sulfide nanocrystalline thin film contains any one of AgBiS2, AgInS2, Cu3BiS3, and CuInS2. A first metal salt, a second metal salt, and a short-chain organic amine are mixed to obtain a metal salt precursor solution; the first metal salt is a transition metal salt, and the second metal salt is at least one of a Group IIIA metal salt and a Group VA metal salt; the short-chain organic amine is at least one of n-butylamine, n-pentylamine, and n-hexylamine; the molar ratio of the first metal salt to the second metal salt is 1:1 to 1.3; the molar ratio of the first metal salt to the short-chain organic amine is 0.25 to 0.40 mmol: 1.00 mL. The metal salt precursor solution is first coated on the substrate surface to obtain a cationic precursor film. After the anionic reaction precursor solution is coated a second time onto the cationic precursor film, it is annealed to obtain the ternary metal sulfide nanocrystalline film; the components of the anionic reaction precursor solution are sulfur source and acetone. The ratio of sulfur source to acetone is 0.5~0.8 mmol:1 mL; the molar ratio of the first metal salt to sulfur source is 1:2~5; The annealing temperature is 120~160℃ and the time is 15~30min.

2. The preparation method according to claim 1, characterized in that, The transition metal salt includes at least one of silver salt and copper salt; The group IIIA metal salts include at least one of indium salts and gallium salts; The Group VA metal salts include bismuth salts.

3. The preparation method according to claim 1, characterized in that, The mixing is performed under ultrasonic conditions; The first coating method is spin coating, the spin coating speed is 2000~4000 rpm, and the time is 20~40s; the mixing and the first coating are both carried out under a protective atmosphere.

4. The preparation method according to claim 1, characterized in that, The sulfur source includes at least one of thiourea and N,N-diphenylthiourea.

5. The preparation method according to claim 1 or 4, characterized in that, The preparation of the anion reaction precursor solution includes: ultrasonically mixing and centrifuging a sulfur source and acetone sequentially; the ultrasonic mixing time is 30-60 min, and the centrifugation speed is 3500-5000 rpm for 5-10 min.

6. The preparation method according to claim 1, characterized in that, The second coating method is spin coating, wherein the spin coating speed is 2000~4000 rpm and the time is 20~40s.

7. The preparation method according to claim 1, characterized in that, The relative humidity for both the second coating and annealing is below 10%.

8. The ternary metal sulfide nanocrystalline thin film prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the ternary metal sulfide nanocrystalline thin film according to claim 8 in solar cells, photodetectors, solar fluorescent concentrators or photocatalysis.

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