Preparation method of lead-free and environment-friendly Cs2TiBr6 double perovskite film

Abstract

The application discloses a kind of preparation methods of lead-free environmental protection Cs2TiBr6 double perovskite film, it includes the following steps: CsBr powder and TiBr4 Powder are added to beaker equipped with gamma-butyrolactone solvent and magnetically stirred to be completely dissolved, then slowly add anhydrous acetonitrile as anti-solvent and constant temperature heating is placed on heating table, after seed microcrystal precipitates, pour out solution, use acetone to flush seed microcrystal after, and dry after standing;Seed microcrystal, CsBr powder and TiBr4 Powder are added to N, N-dimethylformamide solvent, and be loaded into centrifugal tube and centrifuged, pour out supernatant after centrifugation and the precipitate is dried, obtain Cs2TiBr6 microcrystal;Cs2TiBr6 microcrystal is added to the mixed solution of cyclohexane and isopropyl alcohol with certain mass ratio, and magnetically stirred to make microcrystal fully dispersed, obtain Cs2TiBr6 precursor solution;Cs2TiBr6 precursor solution is added dropwise to substrate and spin-coated, then the substrate is placed on heating table and annealed, to obtain Cs2TiBr6 film.The advantages are that, compared with existing film preparation technology, 1) no need of thermal evaporation coating machine and double source co-evaporation process, low cost and simple process;2) will not corrode substrate material;3) the thickness of prepared Cs2TiBr6 film is 8-10 μm, suitable for use in optoelectronic devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of perovskite thin films, and particularly relates to a preparation method of a lead-free and environmentally friendly Cs2TiBr6 double perovskite thin film. BACKGROUND

[0002] In recent years, solar cell devices based on organic-inorganic halide lead-based perovskite materials have made significant progress, and the world record of the photoelectric conversion efficiency of the cell has risen from 3.8% in 2009 to 25.7% in 2022. However, the conventional organic-inorganic halide lead-based perovskite that obtains high efficiency now has environmental toxicity due to containing lead elements, and is unstable due to containing volatile organic cations. Only when the problems of toxicity and instability of the perovskite are solved, can the large-scale commercialization be expected to be realized.

[0003] The Cs2TiBr6 double perovskite material based on the lead-free and environmentally friendly Ti element has been proved to have excellent good photoelectric properties and excellent environmental stability, and is considered to be an ideal material that can replace the conventional organic-inorganic lead-based perovskite. In the existing literature reports, the preparation methods of the Cs2TiBr6 thin film mainly include a high-vacuum thermal evaporation preparation method and a liquid-phase preparation method based on a hydrobromic acid solution. However, the high-vacuum thermal evaporation method has high cost and complex process due to the use of a thermal evaporation coating machine and the adoption of double-source co-evaporation; the liquid-phase preparation method based on the hydrobromic acid solution corrodes the substrate material, and the thickness of the Cs2TiBr6 thin film prepared based on this method (~50 μm) is much higher than the required thickness (1-10 μm) of the photoelectric device, so this preparation method is not conducive to the preparation of the photoelectric device. Therefore, it is necessary to invent a preparation method of the Cs2TiBr6 thin film with simple process, low cost, no corrosion to the substrate material and thin thickness, which is conducive to the commercial production of the Cs2TiBr6 thin film and has important significance for promoting the application of Cs2TiBr6 in photoelectric devices. SUMMARY

[0004] The technical problem solved by the present application is that the existing preparation method of the Cs2TiBr6 thin film has high cost, complex process, corrosion to the substrate material and over-thick prepared thin film. To this end, the present application provides a preparation method of a lead-free and environmentally friendly Cs2TiBr6 thin film, which has the advantages of low cost, simple process and no corrosion to the substrate material, and the prepared thin film has a thickness of only 8-10 μm.

[0005] The technical solution adopted by the present application to solve the above technical problem is as follows: a preparation method of a lead-free and environmentally friendly Cs2TiBr6 double perovskite thin film, characterized in that the preparation method comprises the following steps:

[0006] Step one: CsBr powder and TiBr4 powder are added into a beaker containing γ-butyrolactone solvent and magnetically stirred until completely dissolved, then anhydrous acetonitrile is slowly added as an anti-solvent and placed on a heating table for constant temperature heating, after seed microcrystals precipitate, the solution is discarded, the seed microcrystals are washed with acetone and then left to dry;

[0007] Step two: seed microcrystals, CsBr powder and TiBr4 powder are added into N,N-dimethylformamide solvent, a centrifuge tube is filled and centrifuged, the supernatant after centrifugation is discarded and the precipitate is left to dry, obtaining Cs2TiBr6 microcrystals;

[0008] Step three: Cs2TiBr6 microcrystals are added into a mixed solution of cyclohexane and isopropanol in a certain mass ratio, and magnetically stirred to fully disperse the microcrystals, obtaining a Cs2TiBr6 precursor solution;

[0009] Step four: the Cs2TiBr6 precursor solution is added dropwise to the substrate for spin coating, then the substrate is placed on a heating table for annealing, thereby obtaining a Cs2TiBr6 thin film.

[0010] In the step one, the molar concentrations of CsBr powder and TiBr4 powder in γ-butyrolactone are 0.2 mol / L and 0.1 mol / L respectively, the volume of anhydrous acetonitrile added is 1 / 2-1 of the volume of γ-butyrolactone solvent; the temperature of magnetic stirring is 50-75℃, the stirring speed is 200-500 rpm, and the time is 0.5-1 h; the temperature of constant temperature heating on the heating table is 60-70℃, the time is 12-18 min; the time for standing and drying is 20 min-1 h; the purity of the used CsBr powder is 99.5%, the purity of TiBr4 powder is 98%, and the purity of γ-butyrolactone, anhydrous acetonitrile and acetone is all analytical pure.

[0011] In the step two, the molar amount of seed microcrystals used is 0.15-0.3 mol; the molar amount of CsBr powder and TiBr4 powder used is 1.5-2 times of that in step one, and the volume of N,N-dimethylformamide is 0.9-1.1 times of the volume of γ-butyrolactone in step one; the centrifugation speed is 6000-8000 rpm, the centrifugation time is 8-14 min; the standing and drying time is 15-20 h; the purity of the used CsBr powder is 99.5%, the purity of TiBr4 powder is 98%, and the purity of N,N-dimethylformamide solvent is analytical pure.

[0012] In the third step, the Cs2TiBr6microcrystals are added into a mixed solution of cyclohexane and isopropyl alcohol at a mass percentage of 20-30%, and the volume ratio of cyclohexane to isopropyl alcohol is (4.5-6):1; the heating temperature of magnetic stirring is 20-60℃, the rotating speed of magnetic stirring is 200-500rpm, and the magnetic stirring time is 14-36h; the purity of cyclohexane and isopropyl alcohol used is analytical pure.

[0013] In the fourth step, the spin coating rotating speed is 1500-4000rpm, the acceleration is 1000-4000rpm / s, and the spin coating time is 30-60s; the volume of the Cs2TiBr6precursor solution dropped onto the substrate before spin coating is 60-110μL; the annealing temperature is 80-120℃, and the annealing time is 10-15min.

[0014] In addition, the steps one to four are all carried out in an inert gas glove box.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] 1) No need of a thermal evaporation coating machine and a double-source co-evaporation process, low cost and simple process;

[0017] 2) No corrosion of the substrate material;

[0018] 3) The thickness of the prepared Cs2TiBr6thin film is 8-10μm, which is suitable for use in photoelectric devices. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0020] Figure 1 SEM surface image and optical photo of the Cs2TiBr6double perovskite thin film prepared according to the present application;

[0021] Figure 2 SEM cross-section image of the Cs2TiBr6double perovskite thin film prepared according to the present application;

[0022] Figure 3 XRD spectrum of the Cs2TiBr6double perovskite thin film prepared according to the present application;

[0023] Figure 4 EDS spectrum of the Cs2TiBr6double perovskite thin film prepared according to the present application;

[0024] Figure 5 Elemental proportion of the Cs2TiBr6double perovskite thin film prepared according to the present application. DETAILED DESCRIPTION

[0025] The application will be further described in detail below with reference to the accompanying drawings and specific examples, which are listed below and are not intended to limit the scope of the application.

[0026] Example 1:

[0027] Step one: 426 mg of CsBr powder and 368 mg of TiBr4 powder were added to a beaker containing 1 mL of γ-butyrolactone solvent and magnetically stirred at a speed of 500 rpm for 1 h at a heating temperature of 50°C until complete dissolution, then 0.8 mL of anhydrous acetonitrile was slowly added and placed on a heating table to maintain a constant temperature of 70°C for 15 min, after the seed microcrystals precipitated, the solution was poured out, the microcrystal seeds were washed with acetone and then left to dry for 40 min;

[0028] Step two: 198 mg of seed microcrystals, 766 mg of CsBr powder and 662 mg of TiBr4 powder were added to 900 μL of N,N-dimethylformamide solvent, and a centrifuge tube was filled and centrifuged at a speed of 8000 rpm for 14 min, the supernatant was discarded after centrifugation and the precipitate was left to dry for 20 h to obtain Cs2TiBr6 microcrystals;

[0029] Step three: 237 mg of Cs2TiBr6 microcrystals were added to a mixed solution of 600 μL of cyclohexane and 100 μL of isopropyl alcohol, then magnetically stirred at a speed of 500 rpm for 24 h at a heating temperature of 40°C to obtain a Cs2TiBr6 precursor solution;

[0030] Step four: 70 μL of the precursor solution was added to the substrate, and the spin coater was set to an acceleration of 4000 rpm / s, then spun at a speed of 4000 rpm for 40 s; the spin-coated substrate was removed and placed on a heating table to anneal at a temperature of 100°C for 12 min to obtain a Cs2TiBr6 thin film.

[0031] Here, steps one to four were carried out in an inert gas glove box.

[0032] Figure 1 SEM surface and optical images of the Cs2TiBr6 double perovskite thin film prepared by the preparation method of this example are shown.

[0033] Figure 2 SEM cross-sectional images of the Cs2TiBr6 double perovskite thin film prepared by the preparation method of this example are shown, which shows that the film thickness is about 9 μm.

[0034] Figure 3 XRD spectrum of the Cs2TiBr6 double perovskite thin film prepared by the preparation method of this example is shown.

[0035] Figure 4An EDS spectrum of the Cs2TiBr6 double perovskite film prepared by the preparation method of the embodiment is given.

[0036] Figure 5 An element ratio of the Cs2TiBr6 double perovskite film prepared by the preparation method of the embodiment is given, and it can be seen that the element ratio satisfies Cs:Ti:Br = 2:1:6.

[0037] Embodiment 2:

[0038] Step one: 426 mg of CsBr powder and 368 mg of TiBr4 powder were added to a beaker containing 1 mL of γ-butyrolactone solvent and magnetically stirred at a speed of 500 rpm at a heating temperature of 50 °C for 1 h to make complete dissolution, then 1 mL of anhydrous acetonitrile was slowly added and placed on a heating table to heat at a constant temperature of 70 °C for 15 min, after the seed microcrystals precipitated, the solution was poured out, and the microcrystal seeds were washed with acetone and then dried for 40 min;

[0039] Step two: 119 mg of seed microcrystals and 575 mg of CsBr powder and 497 mg of TiBr4 powder were added to 900 μL of N,N-dimethylformamide solvent, and a centrifuge tube was filled and centrifuged at a speed of 8000 rpm for 14 min, the supernatant was poured out after centrifugation and the precipitate was dried for 20 h to obtain Cs2TiBr6 microcrystals;

[0040] Step three: 203 mg of Cs2TiBr6 microcrystals were added to a mixed solution of 500 μL of cyclohexane and 100 μL of isopropyl alcohol, and then magnetically stirred at a speed of 500 rpm at a heating temperature of 40 °C for 24 h to obtain a Cs2TiBr6 precursor solution;

[0041] Step four: 70 μL of the precursor solution was added to the substrate, and the spin coater was set to an acceleration of 4000 rpm / s, and then spun at a speed of 4000 rpm for 40 s; the spin-coated substrate was taken out and placed on a heating table to anneal at a temperature of 100 °C for 12 min to obtain a Cs2TiBr6 thin film.

[0042] Here, steps one to four are carried out in an inert gas glove box.

[0043] Although the present application has been described in conjunction with the specific embodiments described above, the present application is not limited to the specific embodiments described above, and the specific embodiments described above are merely illustrative, not limiting, and those of ordinary skill in the art can make many modifications under the inspiration of the present application without departing from the purpose of the present application, and these all belong to the protection of the present application.

Claims

1. A method for preparing a lead-free and environmentally friendly Cs2TiBr6 double perovskite thin film, characterized in that, The method comprises the following steps: Step 1: CsBr powder and TiBr4 powder are added into a beaker containing gamma-butyrolactone solvent and magnetically stirred until completely dissolved, then anhydrous acetonitrile is slowly added as an anti-solvent, and the beaker is placed on a heating table for constant temperature heating; after seed microcrystals are precipitated, the solution is poured out, the seed microcrystals are washed with acetone, and then dried by standing; Step 2: the seed microcrystals, CsBr powder and TiBr4 powder are added into N,N-dimethylformamide solvent, and then centrifuged in a centrifuge tube; the supernatant is poured out after centrifugation, and the precipitate is dried by standing to obtain Cs2TiBr6 microcrystals; Step 3: the Cs2TiBr6 microcrystals are added into a cyclohexane and isopropanol mixed solution at a certain mass ratio, and magnetically stirred to fully disperse the microcrystals, to obtain a Cs2TiBr6 precursor solution; Step 4: the Cs2TiBr6 precursor solution is dropped onto a substrate for spin coating, and then the substrate is placed on a heating table for annealing, to obtain a Cs2TiBr6 thin film.

2. The method according to claim 1, wherein the Cs2TiBr6 double perovskite thin film is prepared in a lead-free and environmentally friendly manner. In the step 1, the molar concentrations of CsBr powder and TiBr4 powder in gamma-butyrolactone are 0.2 mol / L and 0.1 mol / L respectively, the volume of anhydrous acetonitrile added is 1 / 2-1 of the volume of gamma-butyrolactone solvent; the temperature of magnetic stirring is 50-75℃, the stirring speed is 200-500 rpm, and the stirring time is 0.5-1 h; the temperature of constant temperature heating on the heating table is 60-70℃, the heating time is 12-18 min; the standing and drying time is 20 min-1 h; the purity of the used CsBr powder is 99.5%, the purity of TiBr4 powder is 98%, and the purity of gamma-butyrolactone, anhydrous acetonitrile and acetone is all analytical pure.

3. The method according to claim 1, wherein the Cs2TiBr6 double perovskite thin film is prepared in a lead-free and environmentally friendly manner. In the step 2, the molar amount of the seed microcrystals used is 0.15-0.3 mol; the molar amount of the used CsBr powder and TiBr4 powder is 1.5-2 times of that in the step 1, and the volume of N,N-dimethylformamide is 0.9-1.1 times of the volume of gamma-butyrolactone in the step 1; the centrifugal speed is 6000-8000 rpm, the centrifugal time is 8-14 min; the standing and drying time is 15-20 h; the purity of the used CsBr powder is 99.5%, the purity of TiBr4 powder is 98%, and the purity of N,N-dimethylformamide solvent is analytical pure.

4. The method according to claim 1, wherein the Cs2TiBr6 double perovskite thin film is prepared in a lead-free and environmentally friendly manner. In the step 3, the Cs2TiBr6 microcrystals are added into a cyclohexane and isopropanol mixed solution at a mass percentage of 20-30%, and the volume ratio of cyclohexane to isopropanol is (4.5-6):1; the heating temperature of magnetic stirring is 20-60℃, the stirring speed is 200-500 rpm, and the stirring time is 14-36 h; the purity of cyclohexane and isopropanol used is analytical pure.

5. The method according to claim 1, wherein the Cs2TiBr6 double perovskite thin film is prepared in a lead-free and environmentally friendly manner. In the fourth step, the spin-coating speed is 1500-4000 rpm, the acceleration is 1000-4000 rpm / s, the spin-coating time is 30-60 s; the volume of the Cs2TiBr6 precursor solution dropped onto the substrate before spin-coating is 60-110 μL; the annealing temperature is 80-120 ℃, and the annealing time is 10-15 min.

6. The method according to claim 1, wherein the Cs2TiBr6 double perovskite thin film is prepared in a lead-free and environmentally friendly manner. The steps one to four are all carried out in an inert gas glove box.

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