阅读说明：本技术 铜锌锡硫薄膜太阳能电池的前驱体溶液及其制备方法与应用 (Precursor solution of copper-zinc-tin-sulfur thin film solar cell and preparation method and application thereof ) 是由 辛颢 张一凡 龚元才 牛传友 邱瑞蝉 于 2020-05-15 设计创作，主要内容包括：本发明公开了一种铜锌锡硫薄膜太阳能电池的前驱体溶液及其制备方法与应用,本发明公开了两类可配制优质前驱体溶液的简单金属配合物,通过使用金属配合物作为前驱体化合物,配制的前驱体溶液稳定性好,可用来制备结晶质量高,薄膜形貌好,无杂质相的铜锌锡硫薄膜吸光材料,以此制备的铜锌锡硫薄膜太阳能电池光电转化效率高。金属配合物的使用,简化了前驱体溶液配制流程,提升了前驱体溶液质量,提高了光伏器件能量转换效率,具有极大的工业应用潜力。(The invention discloses a precursor solution of a copper-zinc-tin-sulfur thin film solar cell, a preparation method and application thereof, and discloses two simple metal complexes capable of preparing a high-quality precursor solution. The use of the metal complex simplifies the preparation process of the precursor solution, improves the quality of the precursor solution, improves the energy conversion efficiency of the photovoltaic device, and has great industrial application potential.)

1. A precursor solution of a copper-zinc-tin-sulfur solar cell is characterized in that: preparing a precursor compound as a solute by using dimethyl sulfoxide (DMSO) or N, N-Dimethylformamide (DMF) as a solvent; the precursor compound consists of a metal complex, a metal salt and thiourea, wherein the metal complex is a copper complex formed by a copper salt and thiourea or a thiourea derivative, a tin complex formed by a tin salt and DMF (dimethyl formamide) or DMSO (dimethyl sulfoxide), and the metal salt is a divalent zinc salt; the precursor compound is dissolved in DMSO or DMF solvent to obtain stable, clear and transparent precursor solution.

2. The precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: the copper complex is formed by copper salt and thiourea or thiourea derivatives, and comprises the following components: complex Cu (Tu) formed by copper halide salt and thiourea₃X is halogen elements including F, Cl, Br and I, and the formed copper complex comprises: cu (Tu)₃Cl，[Cu₂(Tu)₆]Cl₂·2H₂O,Cu(Tu)₃Br; also included are complexes of copper halide salts with thiourea derivatives: cu (DMTu)₃Br，Cu(TMTu)₃Cl，[Cu(ETu)₂Br]₂Wherein DMTu is N, N-dimethylthiourea, TMTU is tetramethylthiourea, and ETu is ethylenethiourea; also comprises a complex Cu formed by copper nitrate salt and thiourea₄(Tu)₁₀(NO₃)·Tu·3H₂O。

3. The precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: the tin complex is selected from Sn (X)_yCl₄，Sn(X)_yF₄,Sn(X)_yBr₄,Sn(X)_yI₄,Sn(X)_y(CH₃COO)₄X is selected from one of DMSO, DMF, ethanol and N-methyl pyrrolidone, and y is a natural number larger than zero.

4. The precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: the zinc salt is a divalent zinc compound, including but not limited to halogen zinc salt, zinc acetate, zinc nitrate, zinc sulfate.

5. The precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: the amount of thiourea species in the precursor solution: the amount of the substance of copper element is not more than 1.

6. The precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: among the precursor compounds:

amount of substance of copper element: the amount of tin element is (1.5-2.5): 1;

amount of zinc species: the amount of tin element is (0.9-1.5): 1;

amount of elemental sulfur species: the sum of the amounts of copper, tin and zinc is (1.0-6.0): 1.

7. the precursor solution of a copper zinc tin sulfide solar cell according to claim 1, wherein: in the precursor solution:

the concentration of the copper element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the tin element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the zinc element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the sulfur element in the solution is 0.15-5 mol/L.

8. The method for preparing a precursor solution for a copper zinc tin sulfide solar cell according to any one of claims 1 to 7, wherein: the specific method for preparing the precursor solution comprises the following steps: dissolving a copper complex and thiourea in a solvent by taking DMSO or DMF as the solvent to prepare a solution I; dissolving a tin complex and a zinc salt in a solvent to prepare a second solution; and mixing the solution I and the solution II to obtain a clear and transparent precursor solution.

9. The method of preparing a precursor solution for a copper zinc tin sulfide solar cell according to claim 8, wherein: the preparation method of the copper complex and the tin complex comprises the following steps:

synthesizing a copper complex: dissolving thiourea in deionized water, adding copper salt into the solution after the thiourea is completely dissolved, wherein the mass ratio of the added thiourea to the copper salt is 3:1, and the temperature of the solution in the reaction process is 70 ℃; after dissolving, filtering the solution, standing, slowly cooling, separating out a target product copper complex crystal from the solution, taking out the crystal product and drying;

synthesizing a tin complex: putting tetravalent tin salt into a round-bottom flask, sealing the flask mouth, and filling an organic compound solvent DMF or DMSO into the flask, wherein the amount ratio of the organic compound to the tin salt in the solvent is 2-20; and (3) reacting the tin salt with a DMF (dimethyl formamide) or DMSO (dimethyl sulfoxide) solvent to generate a large amount of white precipitates, cleaning the precipitates by using ethanol, and drying to obtain the corresponding target product, namely the tin complex.

10. The application of the precursor solution of the copper zinc tin sulfide solar cell according to any one of claims 1 to 7 in the preparation of the copper zinc tin sulfide solar cell is characterized in that: the preparation method of the copper-zinc-tin-sulfur solar cell comprises the following steps:

(1) coating the prepared precursor solution on molybdenum glass in a spinning way, and heating and annealing to generate a copper-zinc-tin-sulfur precursor film;

(2) heating the precursor film in the Se atmosphere to carry out a selenization reaction, and partially or completely replacing S atoms with Se atoms to generate a copper-zinc-tin-sulfur Se film material;

(3) taking out the copper zinc tin sulfur Se film after the selenization reaction, soaking the film in ultrapure water, putting the film into a water jacket beaker containing ammonia water, cadmium sulfate and thiourea solution, reacting under the heating condition, and depositing a layer of CdS on the surface of the copper zinc tin sulfur Se film;

(4) sputtering ZnO and ITO in sequence on the surface of the sample in the step (3) by a magnetron sputtering technology to be used as window layers;

(5) and (4) evaporating metal Ni and Al on the surface of the sample obtained in the step (4) by a thermal evaporation method to be used as a cathode.

Technical Field

The invention belongs to the technical field of new energy photovoltaic power generation, and particularly relates to a precursor solution of a copper-zinc-tin-sulfur thin film solar cell, and a preparation method and application thereof, particularly preparation and application of a photovoltaic device.

Background

The problem of energy shortage is a key problem restricting future development of human beings, the development and utilization of renewable energy are high-quality schemes for solving the problem, and the photovoltaic power generation technology is the most promising development direction in the renewable energy. Over the past several decades, silicon-based solar cells, represented by single crystal silicon and polycrystalline silicon, and multi-compound semiconductor thin film solar cells, represented by cadmium telluride (CdTe) and Copper Indium Gallium Selenide (CIGS), have made significant advances in energy efficiency, and have been successfully produced commercially. The highest photoelectric conversion efficiency obtained by a single crystal silicon cell laboratory at present reaches 26.7%, and the highest photoelectric conversion efficiency obtained by CIGS and CdTe thin film solar cells in the laboratory also reaches 23.35% and 22.1% respectively. However, due to the factors of low extinction coefficient and low defect tolerance of the silicon semiconductor, potential environmental toxicity of Cd element, scarcity of crust resources of In, Ga and Te elements and the like, the manufacturing cost of the photovoltaic devices is high, and the photovoltaic devices are difficult to compete with the traditional energy sources In the market. The Copper Zinc Tin Sulfide (CZTS) material and the Copper Indium Gallium Selenide (CIGS) material have similar crystal structures and optical band gaps, and the absorption coefficient in the visible light range is more than 10⁴The optical band gap is adjustable within the range of 1.0-1.5 eV, the optical band gap is matched with the optimal optical band gap interval of the solar cell material, the theoretical conversion efficiency is higher (32.3%), and meanwhile, the earth of the components of the optical band gap is extremely rich in storage, low in price, safe and nontoxic, and the optical band gap is a novel low-cost light which is expected to replace copper indium gallium selenideA photovoltaic material. The preparation method of the copper-zinc-tin-sulfur film layer material mainly comprises a vacuum method and a solution method. The traditional vacuum preparation method is based on a high vacuum environment, and has high energy consumption and low material utilization rate in the material preparation process. The solution method is based on chemical solution, does not need vacuum environment, has low energy consumption, can be used for large-area film formation, and also has the advantages of improving the material utilization rate, processing at low temperature and the like.

The molecular precursor solution method has high conversion efficiency of the prepared battery due to simple process, and is paid much attention by researchers in recent years. IBM corporation reported 2013 that a precursor solution method based on a hydrazine solvent prepares a copper-zinc-tin-sulfur-selenium solar cell with the energy conversion efficiency of 12.6%. But the explosiveness and high toxicity of hydrazine limit the application of this method. The Hillhouse theme group at Washington university, USA, proposes a precursor solution scheme based on dimethyl sulfoxide solvent with low hazard, but the improvement of the efficiency of the prepared solar cell is limited due to the existence of cation redox reaction in the solution. In view of the above, through research on solution chemistry, the invention discloses a simple, novel, stable, green and environment-friendly precursor solution preparation scheme, which is successfully applied to preparation of copper zinc tin sulfide film selenium film layer materials and copper zinc tin sulfide selenium solar cells, and the prepared copper zinc tin sulfide selenium material has high crystal quality, good appearance and no impurity phase, and the energy conversion efficiency of photovoltaic devices of the material exceeds 10%, thereby indicating remarkable advancement of the invention.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a precursor solution of a Copper Zinc Tin Sulfide (CZTS) thin-film solar cell, a cell preparation method and application thereof, aiming at preparing a high-efficiency copper zinc tin sulfide solar cell, a copper complex formed by copper salt and thiourea is used as a copper precursor, a tin complex generated by tin salt and dimethyl sulfoxide or N, N-dimethylformamide is used as a tin precursor, simple zinc salt is used as a zinc precursor, a stable precursor solution is prepared, a high-quality copper zinc tin sulfide light absorption material without impurity phases is prepared, and the copper zinc tin sulfide thin-film solar cell with high photoelectric conversion efficiency is prepared.

The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:

a precursor solution of a copper-zinc-tin-sulfur solar cell is prepared by taking dimethyl sulfoxide (DMSO) or N, N-Dimethylformamide (DMF) as a solvent and a precursor compound as a solute; the precursor compound consists of a metal complex, a metal compound and thiourea, wherein the metal complex is a copper complex formed by a copper salt and thiourea or a thiourea derivative, a tin complex formed by a tin salt and DMF (dimethyl formamide) or DMSO (dimethyl sulfoxide), and the metal compound is a divalent zinc salt; the precursor compound is dissolved in DMSO or DMF solvent to obtain stable, clear and transparent precursor solution.

Further, the copper complex is a complex formed by a copper salt and thiourea or a derivative of the thiourea, and comprises the following components: complex Cu (Tu) formed by copper halide salt and thiourea₃X is halogen elements including F, Cl, Br and I, and the formed copper complex comprises: cu (Tu)₃Cl，[Cu₂(Tu)₆]Cl₂·2H₂O,Cu(Tu)₃Br; also included are complexes of copper halide salts with thiourea derivatives: cu (DMTu)₃Br，Cu(TMTu)₃Cl，[Cu(ETu)₂Br]₂Wherein DMTu is N, N-dimethylthiourea, TMTU is tetramethylthiourea, and ETu is ethylenethiourea; also comprises a complex Cu formed by copper nitrate salt and thiourea₄(Tu)₁₀(NO₃)·Tu·3H₂O。

Further, the tin complex is selected from Sn (X)_yCl₄，Sn(X)_yF₄,Sn(X)_yBr₄,Sn(X)_yI₄,Sn(X)_y(CH₃COO)₄X is selected from one of DMSO, DMF, ethanol and N-methyl pyrrolidone, and y is a natural number larger than zero.

Further, the zinc salt is a divalent zinc compound, including but not limited to halogen zinc salt, zinc acetate, zinc nitrate, zinc sulfate.

Further, in the precursor solution, the amount of thiourea substance: the amount of copper element is (0-1): 1.

further, in the precursor compound:

amount of substance of copper element: the amount of tin element is (1.5-2.5): 1;

amount of zinc species: the amount of tin element is (0.9-1.5): 1;

amount of elemental sulfur species: the sum of the amounts of copper, tin and zinc is (1.0-6.0): 1.

further, in the precursor solution:

the concentration of the copper element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the tin element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the zinc element in the solution is 0.05 mol/L-5 mol/L;

the concentration of the sulfur element in the solution is 0.15-5 mol/L.

The invention also discloses a preparation method of the precursor solution of the copper-zinc-tin-sulfur solar cell, which comprises the following steps: dissolving a copper complex and thiourea in a solvent with DMSO or DMF as a solvent to prepare a solution I, wherein the amount of thiourea substance: the amount of the substance of copper element is not more than 1; dissolving a tin complex and a zinc salt in a solvent to prepare a second solution; and mixing the solution I and the solution II to obtain a clear and transparent precursor solution.

Further, the preparation method of the copper complex and the tin complex comprises the following steps:

synthesizing a copper complex: dissolving thiourea in deionized water, adding copper salt into the solution after the thiourea is completely dissolved, wherein the mass ratio of the added thiourea to the copper salt is 3:1, and the temperature of the solution in the reaction process is 70 ℃; after dissolving, filtering the solution, standing, slowly cooling, separating out a target product copper complex crystal from the solution, taking out the crystal product and drying;

synthesizing a tin complex: putting tetravalent tin salt into a round-bottom flask, sealing the flask mouth, and filling an organic compound solvent DMF or DMSO into the flask, wherein the amount ratio of the organic compound to the tin salt in the solvent is 2-20; and (3) reacting the tin salt with a DMF (dimethyl formamide) or DMSO (dimethyl sulfoxide) solvent to generate a large amount of white precipitates, cleaning the precipitates by using ethanol, and drying to obtain the corresponding target product, namely the tin complex.

The preparation method of the precursor solution of the high-efficiency copper-zinc-tin-sulfur solar cell and the application of the precursor solution in the preparation of the copper-zinc-tin-sulfur solar cell comprise the following steps:

(1) synthesizing a copper complex: dissolving a certain amount of thiourea in deionized water, adding copper salt into the solution after the thiourea is completely dissolved, wherein the mass ratio of the added thiourea to the copper salt is 3:1, and the temperature of the solution in the reaction process is 70 ℃. After the two substances are basically dissolved, the solution is filtered, kept stand and slowly cooled, and the target product copper complex crystal is separated out from the solution. Filtering to obtain the crystal product, and drying.

(2) Synthesizing a tin complex: putting a certain amount of tetravalent tin salt into a round-bottom flask, sealing the bottle mouth, injecting excessive organic compound DMF or DMSO into the flask, reacting to generate a large amount of white precipitate, filtering, cleaning the precipitate with ethanol, and drying to obtain the target product tin complex.

(3) Preparing a precursor solution: dissolving a copper complex, a tin complex, a divalent zinc compound and thiourea in a solvent by taking DMSO or DMF as the solvent to obtain a clear and transparent precursor solution;

(4) spin-coating the precursor solution obtained in the step 1 on molybdenum glass, and heating and annealing to generate a copper-zinc-tin-sulfur precursor film;

(5) heating the precursor film of copper zinc tin sulfide generated in the step 2 in the Se atmosphere for reaction, and partially or completely replacing S atoms with Se atoms to generate a copper zinc tin sulfide film material;

(6) taking out the copper zinc tin sulfur Se film after the selenization reaction, soaking the film in ultrapure water, putting the film into a water jacket beaker containing ammonia water, cadmium sulfate and thiourea solution, reacting under the heating condition, and depositing a layer of CdS on the surface of the copper zinc tin sulfur Se film; (7) sputtering 50nm of intrinsic zinc oxide (i-ZnO) and 250nm of Indium Tin Oxide (ITO) on the surface of the sample in the step 4 in sequence by a magnetron sputtering technology to be used as window layers;

(8) and (3) sequentially evaporating a grid electrode of 50nm metal Ni and 1 μm Al on the surface of the sample obtained in the step (5) by a thermal evaporation method.

Further, the reaction conditions of spin coating and annealing in step 4 are as follows: the spin-coating rotation speed is 500-8000 rpm, the time is 10-600 s, the annealing temperature is 200-500 ℃, the heating time is 20-120 s, and the spin-coating annealing is repeated for 3-15 times.

Further, step 5, the specific steps of the selenization reaction are as follows:

(5-1) placing the copper-zinc-tin-sulfur film and 0.2-0.5 g of selenium particles in a graphite box, then horizontally and slowly placing the graphite box in a quartz tube, wherein flanges at two ends of the quartz tube are connected with a gas pipeline, and a pressure gauge and a gas valve are connected on the gas pipeline;

(5-2) pumping the gas in the quartz tube to 3 × 10 by a mechanical pump^-2Below Torr, then filling argon until the pressure in the tube is normal pressure;

(5-3) starting a tubular furnace heating program, wherein the target temperature is 500-600 ℃, the heating rate is 0.2-10 ℃/s, and annealing is carried out for 5-30 minutes at the target temperature.

(5-4) after the annealing procedure is ended, naturally cooling to room temperature.

Has the advantages that: compared with the prior art, the preparation method of the precursor solution of the copper-zinc-tin-sulfur thin film solar cell provided by the invention has the following advantages:

1. the invention discloses a synthesis method of two simple metal complexes and is used for preparing a stable precursor solution, the use of the metal complexes keeps the initial valence state of a metal precursor, the oxidation-reduction reaction of monovalent copper ions and tetravalent tin ions is avoided, and the obtained precursor solution has the advantages of excellent quality, good stability and good repeatability.

2. The precursor solution prepared by the invention can be used for preparing a high-quality impurity-phase-free copper-zinc-tin-sulfur light absorption material, and the prepared copper-zinc-tin-sulfur thin-film solar cell has high photoelectric conversion efficiency.

3. The use of the metal complex simplifies the solution preparation process, greatly shortens the solution preparation time and is beneficial to industrial production.

Drawings

FIG. 1 copper complex formed by cuprous chloride and thiourea in the exampleCompound Cu (Tu)₃Physical diagram of Cl.

FIG. 2 shows a tin complex Sn (DMF) formed by tin tetrachloride and N, N-dimethylformamide in example III₂Cl₄The real object diagram of (1).

Fig. 3 is a schematic diagram of a DMSO precursor solution in the first embodiment.

FIG. 4 is a schematic diagram of a DMF precursor solution in the third example.

FIG. 5 is an X-ray diffraction pattern of the precursor thin film in the first embodiment.

Fig. 6 and an X-ray diffraction pattern of the precursor thin film in example three.

Fig. 7 shows an X-ray diffraction pattern of the absorption layer film in example one.

Fig. 8 shows an X-ray diffraction pattern of the absorption layer thin film in example three.

Fig. 9 shows a raman spectrum of the precursor thin film in the first embodiment.

Fig. 10 and a raman spectrum of the precursor thin film in example three.

Fig. 11 shows a raman spectrum of the absorbing layer film in the first embodiment.

Fig. 12 and raman spectrum of the absorption layer thin film in example three.

Fig. 13 is a scanning electron microscope image (film cross section) of the absorption layer film in the first embodiment.

FIG. 14, SEM image of the absorption layer film in example III (film layer cross section).

Fig. 15 is a scanning electron microscope image (film surface) of the absorption layer film in the first example.

Fig. 16 and a scanning electron microscope image (film surface) of the absorption layer film in example three.

Fig. 17 is a voltage-current characteristic curve of the copper zinc tin sulfide selenium solar cell device in the first embodiment under the am1.5g standard solar light intensity.

Fig. 18 is a voltage-current characteristic curve of the copper zinc tin sulfur selenium solar cell device in the third embodiment under the standard solar light intensity of am1.5g.

Detailed Description

The invention discloses a preparation method of a precursor solution of a high-efficiency copper-zinc-tin-sulfur solar cell and preparation and application of a photovoltaic device of the high-efficiency copper-zinc-tin-sulfur solar cell. The invention discloses two simple metal complexes for preparing a precursor solution with excellent stability, and the precursor solution prepared by using the metal complexes as a precursor compound has good stability and repeatability, can be used for preparing a copper-zinc-tin-sulfur film light absorption material with high crystallization quality, good film appearance and no impurity phase, and the prepared copper-zinc-tin-sulfur film solar cell has high photoelectric conversion efficiency. The use of the metal complex simplifies the preparation process of the precursor solution, improves the quality of the precursor solution, improves the energy conversion efficiency of the photovoltaic device, and has great industrial application potential.

The following is a detailed description of the embodiments of the present invention, which is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the scope of the present invention is not limited to the following examples.

The present invention will be better understood from the following examples. However, those skilled in the art will readily appreciate that the specific material ratios, process conditions and results thereof described in the examples are illustrative only and should not be taken as limiting the invention as detailed in the claims.

The first implementation example:

the method comprises the following steps: and (3) preparing a copper complex.

45.67g (0.6mol) of thiourea is weighed and dissolved in 100ml of deionized water, the solution is heated and stirred to keep the temperature of 70 ℃, 19.8g (0.2mol) of cuprous chloride is weighed and added into the solution until the thiourea is completely dissolved, after reaction for 30 minutes, most of the cuprous chloride is dissolved, the solution is heated and filtered, and the filtrate is kept stand and naturally cooled. After a period of time, colorless transparent crystals are separated out from the filtrate, namely the target product copper complex Cu (Tu)₃And Cl, filtering and drying.

Step two: and preparing a tin complex.

Weighing 12.53 g of stannic chloride into a round-bottom flask, sealing the bottle mouth, injecting 50ml of DMSO into the bottle through a syringe, and reacting violently after the two substances are contacted to generate a large amount of whiteAnd (4) precipitating. After the reaction is completed. After the reaction is finished, filtering the reaction solution to obtain white precipitate, washing the white precipitate with ethanol for multiple times, and drying to obtain a target product Sn (DMSO)₄Cl₄。

Step three: and preparing a precursor solution.

8mL of DMSO was measured in a reagent bottle, and 2.0g (6.12mmol) of the copper complex prepared in the first step and 1.667g (4mmol) of the tin complex Sn (DMSO) prepared in the second step were weighed₄Cl₄0.734g (4mmol) of zinc acetate and 0.2g of thiourea were added to the reagent bottle and stirred at room temperature until complete dissolution.

Step four: and (3) preparing a copper zinc tin sulfide (copper zinc tin sulfide) precursor film.

The molybdenum-plated glass is ultrasonically cleaned in acetone and isopropanol for 10 minutes respectively and then dried. And (4) spin-coating the precursor solution prepared in the third step in a glove box, wherein the spin-coating parameters are the spin-coating speed of 1500 rpm and the spin-coating time of 60 s. After the spin coating was completed, the sample was placed on a hot stage at 420 ℃ and annealed for 2 min. Repeating the spin coating-heating process for 7 times to obtain the copper-zinc-tin-sulfur precursor film.

Step five: preparing a copper zinc tin sulfur selenium (copper zinc tin sulfur Se) film.

Placing the two pieces of precursor film samples (2.45cm × 2.45cm) prepared in the fourth step into a graphite box, weighing about 0.35g of Se particles, symmetrically placing the Se particles into a graphite box, tightly closing a valve, and vacuumizing to ensure that the vacuum degree in the tube reaches 3 × 10^-2Argon gas is introduced into the tube after the Torr, and the operations are repeated for 3 times to exhaust the air in the tube, so that the selenization reaction is ensured to be carried out in an anhydrous and oxygen-free environment. Starting a tubular furnace heating program, wherein the target temperature is 550 ℃, the heating rate is 2 ℃/s, and annealing is carried out for 20 minutes at 550 ℃. And naturally cooling the sample to room temperature after the annealing is finished.

Step six: and preparing buffer layer CdS.

And after the selenization reaction is finished, taking out a sample in the graphite ink box, soaking the sample in ultrapure water for 6min, and then depositing the CdS buffer layer by a Chemical Bath Deposition (CBD) method. The first step is as follows: the water bath temperature is set to be 65 ℃, and 22mL of thiourea solution with the concentration of 0.75mol/L, 22mL of cadmium sulfate solution with the concentration of 0.015mol/L and 28mL of ammonia water are respectively measured by using a measuring cylinder. The second step is that: the measured ammonia water and cadmium sulfate solution were mixed in 150mL of ultrapure water, the mixed solution was poured into a water jacket beaker, and then the ultrapure water-soaked sample was placed in the water jacket beaker mixed solution. Circulating water at 65 ℃ is filled into the interlayer of the water jacket beaker for heating and timing is started. The third step: after one minute, the thiourea solution measured in advance was poured into the reaction solution. As the reaction proceeded, the solution changed from clear to light yellow and finally to a yellow translucent suspension. The fourth step: and taking out the sample after the solution reacts for eight minutes, washing the surface of the sample by ultrapure water to remove CdS particles adsorbed on the surface, and then blowing the sample by a nitrogen gun.

Step seven: and preparing a window layer (ZnO/ITO).

Intrinsic zinc oxide (i-ZnO) and Indium Tin Oxide (ITO) are deposited on the sample by a magnetron sputtering method to be used as window layer materials. Sputtering i-ZnO by a magnetron sputtering instrument with sputtering power of 80W and pure argon environment, air pressure of 0.5Pa and film thickness of 50 nm. The sputtering power of the sputtered ITO is 60W, the sputtering pressure of the pure argon environment is 0.5Pa, and the thickness of the film layer is 200 nm.

Step eight: preparation of electrode (Ni/Al).

The cathode of the battery consists of metal Ni and Al and is prepared by a thermal evaporation method. The thicknesses of Ni and Al were 50nm and 500nm, respectively.

The copper-zinc-tin-sulfur precursor film layer and the absorption film layer prepared by the process have no impurity phase, the material crystallinity of the absorption layer is high, the appearance is good, and the energy conversion efficiency of the prepared copper-zinc-tin-sulfur solar cell is 10.9%.

Example two was implemented:

the method comprises the following steps: and (3) preparing a copper complex. The operation method of this step is the same as that of embodiment one.

Step two: 12.53 g of stannic chloride is weighed into a round bottom flask, the mouth of the flask is sealed, 50ml of DMF is injected into the flask by a syringe, and after the two substances are contacted, the reaction is violent, and a large amount of white precipitate is generated. After the reaction is finished, filtering the reaction solution to obtain white precipitate, washing the white precipitate with ethanol for a plurality of times, and drying to obtain a target product Sn (DMF)₂Cl₄。

Step three: of precursor solutionsAnd (4) preparation. 8mL of DMSO was measured in a reagent bottle, and 2.0g (6.12mmol) of the copper complex prepared in the first step and 1.626g (4mmol) of the tin complex Sn (DMF) prepared in the second step were weighed₂Cl₄0.734g (4mmol) of zinc acetate and 0.2g of thiourea were added to the reagent bottle and stirred at room temperature until complete dissolution.

Step four to step eight: the operation method is the same as the first implementation example.

Example three was implemented:

the method comprises the following steps: and (3) preparing a copper complex. The operation method of this step is the same as that of embodiment one.

Step two: 12.53 g of stannic chloride is weighed into a round-bottom flask, the mouth of the flask is sealed, 50ml of DMSO is injected into the flask by a syringe, and after the two substances are contacted, the reaction is violent, and a large amount of white precipitate is generated. After the reaction is completed. After the reaction is finished, filtering the reaction solution to obtain white precipitate, washing the white precipitate with ethanol for multiple times, and drying to obtain a target product Sn (DMSO)₄Cl₄。

Step three: and preparing a precursor solution. 8mL of DMF was taken in a reagent bottle, and 2.0g (6.12mmol) of the copper complex Cu (Tu) prepared in the first step was weighed₃Cl, 1.667g (4mmol) of the tin complex Sn (DMSO) prepared in step two₄Cl₄0.734g (4mmol) of zinc acetate and 0.2g of thiourea were added to the reagent bottle and stirred at room temperature until complete dissolution.

Step four to step eight: the operation method is the same as the first implementation example.

Example four was implemented:

the method comprises the following steps: and (3) preparing a copper complex. The operation method of this step is the same as that of embodiment one.

Step two: 12.53 g of stannic chloride is weighed into a round bottom flask, the mouth of the flask is sealed, 50ml of DMF is injected into the flask by a syringe, and after the two substances are contacted, the reaction is violent, and a large amount of white precipitate is generated. After the reaction is finished, filtering the reaction solution to obtain white precipitate, washing the white precipitate with ethanol for a plurality of times, and drying to obtain a target product, namely a tin complex Sn (DMF)₂Cl₄。

Step three: and preparing a precursor solution. 8mL of DMF was weighed into a reagent bottle, and 2.0g (6.12mmol) of the copper compound prepared in step one was weighedCompound 1.626g (4mmol) of the tin complex Sn (DMF) prepared in step two₂Cl₄0.734g (4mmol) of zinc acetate and 0.2g of thiourea were added to the reagent bottle and stirred at room temperature until complete dissolution.

Step four to step eight: the operation method is the same as the first implementation example.

The embodiment of the invention provides four brand-new preparation methods of precursor solutions for preparing high-efficiency CZTS solar cells, namely, the copper zinc tin sulfide thin film light absorption material with high crystallization quality, good thin film appearance and no impurity phase is prepared by using a metal complex as the precursor solution prepared from a precursor compound, and the high-efficiency copper zinc tin sulfide solar cells are prepared. FIG. 1 and FIG. 2 are photographs showing a copper complex and a tin complex, respectively, which were analyzed by an elemental analyzer to have chemical components of Cu (Tu)₃Cl and Sn (DMF)₂Cl。

Fig. 3 and 4 are photographs of precursor solutions prepared from the two metal complexes in DMSO and DMF solvents, respectively, and it can be observed that both solutions are clear and transparent, have no precipitation or impurity generation, and have good stability, indicating that the solution quality is high.

Fig. 5 and 6 are X-ray diffraction patterns of precursor films formed by spin-coating annealing two precursor solutions, wherein the two precursor films have weak diffraction peaks at diffraction angles 2-Theta of 28.5, 47.3 and 56.1 degrees, and the diffraction peaks respectively correspond to (112), (220) and (312) crystal planes (PDF #26-0575) of copper-zinc-tin-sulfur phase (CZTS), which indicates that CZTS phase is generated in both groups of precursor films. FIGS. 9 and 10 are Raman spectra of the precursor films, with Raman shifts of 337cm for both precursor films^-1Obvious Raman vibration peaks appear at the positions, which correspond to CZTS phases. Both characterization methods indicate that only a single copper zinc tin sulfide phase exists in the precursor film, and no other impurity phase exists, which is beneficial to the subsequent growth and crystallization of the film. Fig. 7 and 8 are X-ray diffraction patterns of the cu-zn-sn-s-se absorption layer thin films formed by selenization of the two precursor thin films, and it can be seen from the diagrams that strong diffraction peaks appear at 2-Theta ═ 27.1, 45.0, and 53.4 of the two cu-zn-sn-s-se absorption layer thin films, and these diffraction peaks respectively correspond to (11) of the cu-zn-sn-se phase (CZTSe)2) The (204) and (312) crystal planes show that the absorption layer film after selenization is all CZTSe phases, and no other impurity phases can be observed.

FIGS. 11 and 12 show Raman spectra of the CZTSSe absorber films, where the Raman shifts of the two precursor films are 172, 193, 231cm^-1Obvious Raman vibration peaks appear at the positions, which correspond to copper zinc tin selenium (CZTSe), and Raman vibration peaks without other impurity phases can be observed. This indicates that the prepared absorption layer film is a high-quality copper-zinc-tin-sulfur-selenium film. Scanning electron micrographs of the high crystallinity, flat, dense, unphased absorber films observed in figures 13, 14, 15, and 16 further demonstrate the high quality of the absorber films produced by the examples. Two groups of light absorption film layers are prepared into a solar cell device and subjected to photovoltaic performance test, voltage-current characteristic curves of the solar cell device are shown in figures 17 and 18, photoelectric conversion efficiency of the two devices exceeds 10%, and the international advanced level is achieved.

In conclusion, the technical scheme of the invention prepares the stable, clear and transparent high-quality precursor solution, and applies the precursor solution to the preparation of the copper-zinc-tin-sulfur-selenium film material and the photovoltaic device, and finally, the copper-zinc-tin-sulfur-selenium film material with high crystallization quality, good appearance and no impurity phase and the photovoltaic device with the energy conversion efficiency of more than 10 percent are obtained, thereby showing the remarkable advancement of the invention.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.