A multi-component mixed solvent, copper-zinc-tin-sulfur-selenium thin film, and a preparation method and application thereof

Abstract

The application relates to the technical field of battery films, in particular to a multi-component mixed solvent, a copper-zinc-tin-sulfur-selenium film and a preparation method and application thereof. The multi-component mixed solvent is a mixture of one or two components of gamma-butyrolactone and isopropyl alcohol and dimethyl sulfoxide. The preparation method of the copper-zinc-tin-sulfur-selenium film comprises the following steps: copper nitrate is added into the multi-component mixed solvent and stirred until clear; zinc acetate is added and stirred until clear; stannous chloride is added and stirred until clear; and then thiourea is added and stirred until clear to obtain a precursor solution; the precursor solution is coated on molybdenum-coated glass by spin coating, blade coating or / and inkjet printing of the precursor solution, and then the precursor film is sulfurized / selenized by high-temperature heating and cooling to obtain the copper-zinc-tin-sulfur-selenium film. The application cooperates dimethyl sulfoxide, gamma-butyrolactone and isopropyl alcohol, reduces the usage amount of harmful solvents, and applies the prepared film to a solar cell, and the efficiency can reach 7.82%.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell thin film technology, and in particular to a multi-component mixed solvent, copper-zinc-tin-sulfur-selenium thin film, its preparation method, and its application. Background Technology

[0002] With the rapid development of science and technology, global energy demand has risen sharply. Traditional fossil fuel energy requires the massive extraction of Earth's mineral resources, making it difficult to sustain long-term energy supply and causing irreparable damage to the ecological environment. Therefore, in order to protect the Earth's environment and achieve low-carbon goals, seeking sustainable and clean energy for energy transition is imperative. Solar energy is an inexhaustible, inexpensive, and environmentally friendly new energy source. Converting solar energy into electricity through photovoltaic technology can improve energy production and benefit society. Currently, various solar cells are flourishing, including crystalline silicon solar cells, which are already widely commercialized, common gallium arsenide, cadmium telluride, and copper indium gallium selenide (CIGS) thin-film solar cells, and various new solar cells still in the research stage, such as perovskite, copper zinc tin sulfide selenide (CZTSSe) thin-film materials. Among them, CZTSSe thin-film materials have a similar structure to CIGS materials, which have currently achieved a high conversion efficiency of 23.6%, but due to the presence of rare metals indium and gallium, their high cost is not conducive to industrial production. CZTSSe materials have a wide tunable bandgap range (1.0–1.5 eV) and a high absorption coefficient (>10). 4 cm -1 Furthermore, it contains non-toxic elements, is abundant, and has a low cost, making it an ideal material for solar cells. Theoretical calculations show that the theoretical efficiency of this type of solar cell can reach as high as 32.4%. In conclusion, CZTSSe material is a very promising photovoltaic material, and this type of solar cell has broad application prospects and social value.

[0003] The preparation methods of CZTSSe thin films can be mainly divided into vacuum methods and non-vacuum methods. Vacuum methods mainly include thermal evaporation and magnetron sputtering. Non-vacuum methods are mainly solution methods, which have been widely used and rapidly developed due to their convenient operation and low preparation cost. Currently, the highest efficiency of CZTSSe thin film solar cells at 13.0% (Gong, Y., Zhu, Q., Li, B. et al. Nat Energy 7, 966–977 (2022)) was prepared by spin-coating solution method.

[0004] In solution preparation, commonly used solvents include dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), ethanolamine, ethylenediamine, etc. The current highest battery efficiency of 13.0% uses dimethyl sulfoxide as a solvent. This type of solvent has strong permeability to biological skin, and long-term use can easily cause harm to health and aggravate environmental pollution. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a multi-component mixed solvent, which reduces its harm to the human body by adding environmentally friendly solvents. It has good stability when used to dissolve copper, zinc and tin, and can improve battery efficiency when used in batteries.

[0007] Accordingly, the present invention also provides a method for preparing copper-zinc-tin-sulfur-selenium thin films using a multi-component mixed solvent;

[0008] Accordingly, the present invention also provides an application of the above-mentioned copper-zinc-tin-sulfur-selenium thin film in solar cells.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] In a first aspect, the present invention provides a multi-component mixed solvent for dissolving copper, zinc and tin metal salts, which is one or two components of γ-butyrolactone and isopropanol, mixed with dimethyl sulfoxide.

[0012] Optionally, dimethyl sulfoxide, γ-butyrolactone, and isopropanol are in a volume ratio of 7–9:1–2:1–2.

[0013] Secondly, the present invention also provides a method for preparing copper-zinc-tin-sulfur-selenium thin films using a multi-component mixed solvent, comprising the following steps:

[0014] Preparation of S1 precursor solution: Copper nitrate was added to the multi-component mixed solvent and stirred until clear; zinc acetate was added and stirred until clear; stannous chloride was added and stirred until clear; thiourea was added and stirred until clear to obtain the precursor solution.

[0015] S2 The precursor solution is spin-coated, blade-coated or / and inkjet-printed onto molybdenum-plated glass, and then the precursor film is sulfidated / selenized by heating at high temperature and then cooling to obtain a copper-zinc-tin-sulfur-selenium film.

[0016] Optionally, sulfur / selenization involves placing the precursor film and the sulfur / selenization source in a sealed environment filled with inert gas, heating to 400–800°C, holding at that temperature for 3–180 minutes, and then naturally cooling to complete the sulfur / selenization process and obtain a copper-zinc-tin-sulfur-selenium film.

[0017] Optionally, the molar ratio of Zn to Sn in the precursor solution is 0.7 to 2.0:1; and the molar ratio of Cu to Zn+Sn is 0.4 to 1.4:1.

[0018] Thirdly, the present invention also provides copper-zinc-tin-sulfur-selenium thin films prepared by the methods described in any of the above embodiments.

[0019] Fourthly, the present invention also provides the application of the copper-zinc-tin-sulfur-selenium thin film in solar cells in any of the above embodiments.

[0020] (III) Beneficial Effects

[0021] The beneficial effects of this invention are: the multi-component mixed solvent for dissolving copper, zinc and tin metal salts of this invention, through the combination of dimethyl sulfoxide, γ-butyrolactone and isopropanol, reduces the amount of harmful solvents used, and when the zinc-tin-sulfur-selenium thin film is applied to solar cells, the efficiency can reach more than 7.82%.

[0022] Although the present invention introduces isopropanol, which is difficult to dissolve copper, zinc and tin metal salts, the combination of the components of the present invention can dissolve copper, zinc and tin metal salts to obtain a clear solution.

[0023] In this invention, the combination of dimethyl sulfoxide, γ-butyrolactone, and isopropanol, compared to the combination of other solvents in this invention, has improved the efficiency of solar energy. Attached Figure Description

[0024] Figure 1 A schematic diagram of a copper-zinc-tin-sulfur-selenium solar cell structure;

[0025] Figure 2 The X-ray diffraction pattern measured in Experiment 1 of this invention;

[0026] Figure 3 This is a SEM image of the copper-zinc-tin-sulfur-selenium thin film surface measured in Experiment 2 of this invention;

[0027] Figure 4 This is the JV diagram of the battery sample measured in Experiment 3 of this invention. Detailed Implementation

[0028] To better explain and facilitate understanding of the invention, exemplary embodiments of the invention will be described in more detail below. While exemplary embodiments of the invention are shown below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention can be understood more clearly and thoroughly, and that the full scope of the invention can be conveyed to those skilled in the art.

[0029] Example 1

[0030] This embodiment provides a mixed solvent for dissolving copper, zinc and tin metal salts, which is a mixture of dimethyl sulfoxide (DMSO), γ-butyrolactone (γ-GBL) and isopropanol (IPA) in a volume ratio of 8:1:1.

[0031] Example 2

[0032] This embodiment provides a mixed solvent for dissolving copper, zinc and tin metal salts, which is a mixture of dimethyl sulfoxide (DMSO), γ-butyrolactone (γ-GBL) and isopropanol (IPA) in a volume ratio of 9:1.5:2.

[0033] Example 3

[0034] This embodiment provides a mixed solvent for dissolving copper, zinc and tin metal salts, which is a mixture of dimethyl sulfoxide (DMSO), γ-butyrolactone (γ-GBL) and isopropanol (IPA) in a volume ratio of 7:2:1.5.

[0035] Example 4

[0036] This embodiment provides a mixed solvent for dissolving copper, zinc and tin metal salts, which is a mixture of dimethyl sulfoxide (DMSO) and γ-butyrolactone (γ-GBL) in a volume ratio of 8:1.

[0037] Example 5

[0038] This embodiment provides a mixed solvent for dissolving copper, zinc and tin metal salts, which is a mixture of dimethyl sulfoxide (DMSO) and isopropanol (IPA) in a volume ratio of 8:1.

[0039] Example 6

[0040] This embodiment provides a method for dissolving copper-zinc-tin metal salts to obtain a clear solution (precursor solution). The steps are as follows: Weigh 0.7188g of copper nitrate trihydrate in air and place it in a glass bottle equipped with a magnetic stir bar. Use a pipette to add 2.0ml of dimethyl sulfoxide (DMSO), 0.25ml of γ-butyrolactone (γ-GBL), and 0.25ml of isopropanol (IPA) in sequence (corresponding to the solvent ratio of DMSO:γ-GBL:IPA = 8:1:1 in Example 1; in other embodiments, the corresponding solvents can also be added in the ratio of Examples 2-4). Stir at room temperature until completely dissolved to obtain a deep blue transparent clear solution. Then add 0.4514g of zinc acetate and stir until clear. Add 0.4626g of stannous chloride dihydrate and stir until dissolved and clear. Continue to add 0.7479g of thiourea and stir to obtain a pale yellow clear transparent solution.

[0041] In the solution obtained in this embodiment, the molar ratio of Zn to Sn is 1.2, the molar ratio of Cu / (Zn+Sn) is 0.66, and the total molar concentration of all metal salts is 2.8M.

[0042] Example 7

[0043] This embodiment provides a method for preparing copper-zinc-tin-sulfur-selenium thin films from the precursor solution obtained in Example 6, the steps of which are as follows:

[0044] S1. Repeat the following steps S11-S35 11 times to obtain the precursor film:

[0045] The precursor solution obtained in any one of Examples 1-3 was dropped onto the molybdenum glass surface; after the first spin coating at 2000 r / min for 60 s, a second spin coating at 4000 r / min for 30 s was continued; the temperature was raised to 300°C and held for 2 min, and then cooled to room temperature.

[0046] S2 Take 350mg of selenium powder, spread it in the center of the bottom of the graphite box, place the obtained precursor film on the graphite box partition, and put it into the annealing furnace;

[0047] Evacuate to below 30 mtorr and close the valve. Then introduce nitrogen gas to raise the vacuum to 500 Torr and close the nitrogen gas valve. Repeat the vacuuming and nitrogen gas introduction steps three times to ensure that the selenization reaction is carried out under oxygen-free nitrogen protection.

[0048] Adjust the inlet and outlet valves to maintain the gas pressure inside the quartz tube of the return furnace at one atmosphere. Heat to 560°C at a heating rate of 100°C / min and hold for 15 minutes to replace oxides with selenides and further generate copper-zinc-tin-sulfur-selenium thin films.

[0049] In this embodiment, replacing selenium powder with sulfur powder can produce the corresponding copper-zinc-tin-sulfur thin film, or replacing selenium powder with a mixture of sulfur powder and selenium powder can produce the corresponding copper-zinc-tin-sulfur-selenium thin film.

[0050] Example 8

[0051] This embodiment provides the application of the copper-zinc-tin-sulfur-selenium thin film prepared in Example 7 in solar cells, and the steps are as follows:

[0052] Etching treatment of S1 copper-zinc-tin-sulfur-selenium thin film: The copper-zinc-tin-sulfur-selenium thin film was immersed in 5 vol% dilute hydrochloric acid for 10 min under 75℃ water bath conditions, rinsed repeatedly with deionized water and dried with nitrogen gas. At room temperature, it was immersed in 20 wt% ammonium sulfide solution for 3 min, rinsed repeatedly with deionized water and dried with nitrogen gas.

[0053] S2 Chemical Bath Deposition Method: The etched copper-zinc-tin-sulfur-selenium thin film is placed in a 50ml volumetric flask and 40ml of ultrapure water, 3.75ml of 0.019M cadmium acetate ammonia solution, and 5ml of 1M thiourea solution are added sequentially. Finally, ultrapure water is added to make up to 50ml to prepare the soaking solution. The soaking solution is poured out and kept at 75℃ in a water bath while being stirred at 100-300rpm. Under stirring, the copper-zinc-tin-sulfur and / or selenium thin film is completely immersed in the soaking solution for 7min under suspension for deposition. After removal, it is repeatedly rinsed with deionized water and dried with nitrogen gas. A CdS film with a thickness of 50-70nm can be obtained on the surface of the copper-zinc-tin-sulfur-selenium thin film.

[0054] S3 sequentially prepared a 50 nm ZnO layer by RF sputtering of the obtained CdS thin film, a 300 nm ITO window layer by DC sputtering, and finally prepared an Ag grid top electrode by thermal evaporation to obtain a CZTSSe thin-film solar cell. Figure 1 The diagram shows the structure of a copper-zinc-tin-sulfur-selenium solar cell.

[0055] Experiment 1: The copper-zinc-tin-selenium thin film prepared by the method in Example 7 was analyzed by XRD diffraction. Figure 2 The diffraction pattern shown;

[0056] In the figure, DMSO+γ-GBL represents the method of Example 6, in which the mixed solvent is a mixture of 2.0 ml of dimethyl sulfoxide (DMSO) and 0.25 ml of γ-butyrolactone (γ-GBL) (i.e., mixed according to the ratio of Example 4), and the diffraction pattern of the copper zinc tin sulfur selenium thin film prepared by the method of Example 5 is determined by XRD diffraction.

[0057] DMSO+γ-GBL+IPA represents the XRD pattern of a copper-zinc-tin-sulfur-selenium thin film prepared using the method of Example 7, in which the mixed solvent is a mixture of 2.0 ml of dimethyl sulfoxide (DMSO), 0.25 ml of γ-butyrolactone (γ-GBL), and 0.25 ml of isopropanol (IPA).

[0058] DMSO+IPA represents the method of Example 6, in which the mixed solvent is a mixture of 2.0 ml of dimethyl sulfoxide (DMSO) and 0.25 ml of isopropanol (IPA) (i.e., mixed according to the ratio of Example 5), and the diffraction pattern of the copper-zinc-tin-sulfur-selenium thin film prepared using the method of Example 7 is determined by XRD diffraction.

[0059] In the method of Example 6, DMSO was used as the mixed solvent, which was 2.5 ml of dimethyl sulfoxide. The diffraction pattern of the copper-zinc-tin-sulfur-selenium thin film prepared by the method of Example 5 was determined by XRD diffraction.

[0060] To facilitate data comparison and analysis, the diffraction intensities in the XRD patterns have been normalized: the relative intensities of the remaining peaks are calculated with the highest peak intensity in the curve as 100%.

[0061] The sharp diffraction peaks in the XRD pattern are close to those in the standard CZTSe diffraction pattern (JCPDS#52-0868). Due to the presence of a certain amount of sulfur in the film, smaller S atoms occupy larger Se atomic sites within the unit cell, reducing the unit cell parameter. According to the Bragg diffraction equation (2dsinθ=nλ), the diffraction peaks shift to higher angles. This indicates that the main component of the crystalline films prepared using different mixed solvents is CZTSSe phase. Furthermore, the SEM images of the film surface prepared using a mixed solvent of DMSO and IPA demonstrate that this mixed solvent can yield well-crystallized CZTSSe crystalline films.

[0062] Experiment 2: SEM images of the copper-zinc-tin-sulfur-selenium thin film prepared by mixing and dissolving 2.0 ml of dimethyl sulfoxide (DMSO) and 0.25 ml of isopropanol (IPA) in Experiment 1 of this invention are shown below. Figure 3 As shown, from Figure 3 From this, we can see that the thin film has obvious crystal particles, and the crystal size and compactness are directions that need to be further improved.

[0063] Experiment 3: Using different solvents from Experiment 1 of this invention, corresponding copper-zinc-tin-sulfur-selenium thin films were prepared using the method of Example 4, and CZTSSe solar cells were prepared using the method of Example 6; For example... Figure 4 The image shows the JV diagram and cell parameters obtained from testing a cell sample using a standard solar cell tester. It can be seen that the ternary mixed solvent of Example 1 of this invention can produce a CZTSSe solar cell with an efficiency of 7.82%. Examples and data graphs show: Figure 4 The JV data show that all the above examples can prepare effective CZTSSe thin-film solar cells, and it was found that the addition of IPA to the multi-component mixed solvent can improve the efficiency of CZTSSe thin-film solar cells prepared by solution method.

[0064] The efficiency of DMSO+γ-GBL is 6.05%, while that of DMSO is 6.50%, indicating that the addition of γ-GBL significantly reduces efficiency.

[0065] The efficiency of DMSO+γ-GBL+IPA is 7.82%, while that of DMSO+IPA is 7.36%. This shows that the addition of γ-GBL significantly improves the efficiency of DMSO+γ-GBL+IPA in the presence of IPA. This indicates that IPA changes the effect of γ-GBL on the efficiency of solar cells from negative to positive. Thus, the mixed solvent of DMSO+γ-GBL+IPA in Example 1 of this invention achieves a better technical effect in improving cell efficiency.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-component mixed solvent for dissolving copper-zinc-tin metal salts, characterized by: It is a mixture of γ-butyrolactone, isopropanol and dimethyl sulfoxide; The dimethyl sulfoxide, the γ-butyrolactone, and the isopropanol are in a volume ratio of 7~9:1~2:1~2.

2. The method for preparing copper zinc tin sulphur selenide thin film by using the multi-component mixed solvent according to claim 1, characterized in that: It includes the following steps: Preparation of S1 precursor solution: Copper nitrate was added to the multi-component mixed solvent and stirred until clear; zinc acetate was added and stirred until clear; stannous chloride was added and stirred until clear; thiourea was added and stirred until clear to obtain the precursor solution. S2 applies the precursor solution onto molybdenum-coated glass via spin coating, blade coating, or / and inkjet printing, and then sulfidates and selenizes the precursor film by heating at high temperature and then cooling to obtain a copper-zinc-tin-sulfur-selenium film.

3. The method for preparing copper-zinc-tin-sulfur-selenium thin films using a multi-component mixed solvent as described in claim 2, characterized in that: The sulfidation and selenization are carried out by placing the precursor film, sulfidation source, and selenization source in a sealed environment filled with inert gas, heating to 400~800℃, holding at that temperature for 3~180min, and then naturally cooling to complete the sulfidation and selenization to obtain a copper-zinc-tin-sulfur-selenium film.

4. The method of claim 2, wherein the multi-component mixed solvent is prepared by mixing a solvent having a high dielectric constant and a solvent having a low dielectric constant. The precursor solution contains Zn and Sn in a molar ratio of 0.7 to 2.0:1; and Cu and Zn+Sn in a molar ratio of 0.4 to 1.4:

1.

5. A copper-zinc-tin-sulfur-selenium thin film prepared by the method according to any one of claims 2-4.

6. The application of the copper-zinc-tin-sulfur-selenium thin film as described in claim 5 in a solar cell.

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