Perovskite thin film and preparation method and application thereof

Abstract

The invention provides a perovskite thin film and a preparation method and application thereof. The preparation method of the perovskite thin film comprises the following steps: S1, preparing a mixed solution containing a perovskite precursor solution and an additive; s2, coating a substrate with the mixed solution to form a liquid film, and sequentially carrying out anti-solvent treatment and annealing treatment on the liquid film to obtain a perovskite thin film; wherein the perovskite thin film is an ABX3 type organic-inorganic hybrid perovskite thin film; the perovskite precursor solution contains organic cations, lead ions and halide ions which form the ABX3 type organic-inorganic hybrid perovskite thin film, and the organic cations are selected from methylamine ions and / or formamidine ions; the structure of the additive contains phosphonyl and ester groups. Based on the preparation method of the perovskite thin film, the photoelectric conversion efficiency of the perovskite thin film can be improved.

Description

Technical Field

[0001] The present invention relates to a solar cell, and in particular to a perovskite film and a preparation method and application thereof. Background Art

[0002] Metal halide perovskites have attracted widespread attention due to their low cost, simple preparation, long carrier diffusion distance, and adjustable band gap, and are considered to be the most promising new generation of photovoltaic materials. At present, the photoelectric conversion efficiency of perovskite solar cells has reached 26.7%, close to the mainstream crystalline silicon solar cells in the market. However, due to the low defect formation energy in perovskite films, vacancy defects and surface dangling bonds are easily formed during the solution preparation process. These defect sites act as charge recombination centers, causing non-radiative recombination in solar cells, which seriously affects the photoelectric conversion efficiency of the device. Therefore, it is of great significance to develop high-quality perovskite films with low defect density. Summary of the invention

[0003] The main purpose of the present invention is to provide a perovskite film and a preparation method and application thereof, so as to solve the problem of low photoelectric conversion efficiency of the perovskite film in the prior art.

[0004] In order to achieve the above object, according to one aspect of the present invention, a method for preparing a perovskite film is provided, comprising the following steps:

[0005] Step S1, preparing a mixed solution including a perovskite precursor solution and an additive;

[0006] Step S2, coating the mixed solution on a substrate to form a liquid film, and sequentially performing anti-solvent treatment and annealing treatment on the liquid film to obtain a perovskite film;

[0007] Wherein, the perovskite film is an ABX3 type organic-inorganic hybrid perovskite film; the perovskite precursor solution contains organic cations, lead ions and halide ions that form the ABX3 type organic-inorganic hybrid perovskite film, and the organic cations are selected from methylamine ions and / or formamidine ions;

[0008] The additive structure has a phosphono group and an ester group.

[0009] Furthermore, the additive is a phosphonoacetate compound.

[0010] Preferably, the additive is selected from one or more of diethyl methyl phosphonoacetate, triethyl phosphonoacetate, and trimethyl phosphonoacetate;

[0011] Furthermore, the volume ratio of the additive to the perovskite precursor solution is (0.1% to 10%):1.

[0012] Furthermore, the volume ratio of the additive to the perovskite precursor solution is (0.5% to 5%):1.

[0013] Furthermore, the concentration of the perovskite precursor solution is 0.5 mol / L to 2 mol / L based on ABX3.

[0014] Further, the solvent in the perovskite precursor solution is selected from one of N,N-dimethylformamide and dimethyl sulfoxide or a mixture of the two in any proportion;

[0015] Preferably, the solvent in the perovskite precursor solution is a mixed solvent formed by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (1-4):(1-2).

[0016] Furthermore, in step S2, the mixed liquid is coated on the substrate by spin coating to form a liquid film;

[0017] Preferably, the spin coating speed is 2000 rpm to 6000 rpm, and the spin coating time is 5 s to 50 s.

[0018] Furthermore, in the anti-solvent treatment, the anti-solvent is selected from one or more of toluene, chlorobenzene, cyclohexane, and ethyl acetate.

[0019] Furthermore, in the annealing treatment, the annealing temperature is 100° C. to 300° C., and the annealing time is 5 min to 60 min.

[0020] According to another aspect of the present invention, a perovskite film is provided, which is prepared according to the above method for preparing a perovskite film.

[0021] According to another aspect of the present invention, a solar cell is provided, comprising a light absorbing layer, wherein the light absorbing layer comprises the above perovskite film.

[0022] By applying the technical solution of the present invention, by adding an additive having a phosphonyl group and an ester group to a perovskite precursor solution, the crystallinity of the perovskite film can be improved, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. In addition, its molecular structure contains a phosphonyl group and an ester group. During the formation of the perovskite film, the phosphonyl group can form a hydrogen bond with the organic cations in the perovskite material to fix the cations; the ester group can coordinate with the lead ions to passivate the low-coordinated lead ions, thereby reducing the defects in the perovskite lattice, improving the quality of the perovskite film, and improving the photoelectric conversion efficiency of the perovskite solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 A process flow chart of the method for preparing the perovskite thin film according to the present invention is shown. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] As described in the background art, the prior art has the problems of many defects in perovskite films and low photoelectric conversion efficiency. In order to solve the above problems, Figure 1 According to one aspect of the present invention, a method for preparing a perovskite film is provided, comprising the following steps:

[0027] Step S1, preparing a mixed solution including a perovskite precursor solution and an additive;

[0028] Step S2, coating the mixed solution on a substrate to form a liquid film, and sequentially performing anti-solvent treatment and annealing treatment on the liquid film to obtain a perovskite film;

[0029] Wherein, the perovskite film is an ABX3 type organic-inorganic hybrid perovskite film; the perovskite precursor solution contains organic cations, lead ions and halide ions that form the ABX3 type organic-inorganic hybrid perovskite film, and the organic cations are selected from methylamine ions and / or formamidine ions;

[0030] The additive structure has a phosphono group and an ester group.

[0031] ABX3 type perovskite film is a material with unique optical and electrical properties, and is widely used as a light absorption layer in solar cells. In the technical solution of the present invention, the perovskite precursor solution contains formamidinium ions (FA + ) and / or methylamine ion (MA + ), lead ion (Pb 2+ ) and halide ions (X - , X can be Cl, Br, I, etc.), formamidinium ion (FA + ) and other organic cations, lead ions (Pb 2+ ) and halide ions (X - ) through coordination, forming an ABX3 type organic-inorganic hybrid perovskite structure, for example, FAPbX3, which has a high light absorption coefficient, long carrier diffusion length and adjustable band gap, and is a highly efficient photoelectric conversion material.

[0032] Based on the preparation method of the perovskite film of the present invention, by adding an additive having a phosphonyl group and an ester group to the perovskite precursor solution, the crystallinity of the perovskite film can be improved, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. In addition, its molecular structure contains a phosphoryl group and an ester group. During the formation of the perovskite film, the phosphoryl group can form a hydrogen bond with the organic cation in the perovskite material to fix the cation; the ester group can coordinate with the lead ion to passivate the low-coordinated lead ion, thereby reducing the defects in the perovskite lattice, improving the quality of the perovskite film, and improving the photoelectric conversion efficiency of the perovskite solar cell.

[0033] In some embodiments, the additive is a phosphonoacetate compound, which is beneficial to improve the crystallinity of the film and reduce crystal defects; preferably, the additive is selected from one or more of diethyl methyl phosphonoacetate, triethyl phosphonoacetate, and trimethyl phosphonoacetate.

[0034] In some embodiments, the volume ratio of the additive to the perovskite precursor solution is (0.1% to 10%):1.

[0035] In the technical solution of the embodiment of the present invention, controlling the additive within the above range can effectively form a stable coordination bond with the lead ions in the perovskite material, thereby reducing lattice defects and improving the uniformity of the film.

[0036] In one embodiment, in order to further improve the photoelectric conversion efficiency of the perovskite film, the volume ratio of the additive to the perovskite precursor solution is (0.5% to 5%):1.

[0037] In one embodiment, in order to further improve the photoelectric conversion efficiency of the perovskite film, the concentration of the perovskite precursor solution is 0.5 mol / L to 2 mol / L based on ABX3.

[0038] In some embodiments, the solvent in the perovskite precursor solution is selected from N,N-dimethylformamide, dimethyl sulfoxide, or a mixture of the two in any proportion.

[0039] In the technical solution of the embodiment of the present invention, N,N-dimethylformamide and dimethyl sulfoxide have good solubility and volatility, can effectively dissolve the perovskite material, and volatilize quickly during the spin coating process, which is conducive to the rapid formation of the thin film and the formation of a uniform film layer.

[0040] In one embodiment, in order to form a more uniform perovskite thin film layer, the solvent in the perovskite precursor solution is a mixed solvent formed by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (1-4): (1-2).

[0041] In some embodiments, in step S2 , the mixed liquid is coated on the substrate by spin coating to form a liquid film.

[0042] In one embodiment, the spin coating speed is 2000 rpm to 6000 rpm, and the spin coating time is 5 s to 50 s.

[0043] In some embodiments, in the anti-solvent treatment, the anti-solvent is selected from one or more of toluene, chlorobenzene, cyclohexane, and ethyl acetate, including but not limited to the above anti-solvents.

[0044] In the technical solution of the embodiment of the present invention, the anti-solvent treatment uses solvents such as toluene, chlorobenzene, cyclohexane, ethyl acetate, etc. that are insoluble in the perovskite material, which is beneficial to quickly reduce the solvent concentration in the solution and promote the rapid precipitation and crystallization of the perovskite material.

[0045] In one embodiment, the anti-solvent treatment includes: spin coating the anti-solvent on the liquid film according to a volume ratio of the anti-solvent to the liquid film of (2-4):1.

[0046] In the technical solution of the embodiment of the present invention, controlling the volume ratio of the anti-solvent (such as toluene, chlorobenzene or cyclohexane) to the liquid film (for example, the solvent is N,N-dimethylformamide or dimethyl sulfoxide) within the above range is beneficial to balance the rapid formation and uniform crystallization of the perovskite film and avoid film defects caused by too fast evaporation of the solvent.

[0047] In some embodiments, during the annealing process, the annealing temperature is 100° C. to 300° C., and the annealing time is 5 min to 60 min.

[0048] In the technical solution of the embodiment of the present invention, under the above-mentioned annealing conditions, it is beneficial to improve the crystallinity and density of the perovskite film and enhance the photoelectric performance of the film.

[0049] According to another aspect of the present invention, a perovskite film is provided, which is prepared according to the above method for preparing a perovskite film.

[0050] According to another aspect of the present invention, a solar cell is provided, comprising a light absorbing layer, wherein the light absorbing layer comprises the above perovskite film.

[0051] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0052] Example 1

[0053] A method for preparing a solar cell comprises the following steps:

[0054] Step 1: Clean the FTO glass substrate with acetone, isopropanol and deionized water in sequence, blow dry and set aside.

[0055] Step 2: Prepare a NiOx hole transport layer on a FTO glass substrate by magnetron sputtering and annealing, with a thickness of 30 nm, an annealing temperature of 300° C., and an annealing time of 30 min.

[0056] Step 3: Prepare 1.5 mol / L (FA 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 )3 perovskite precursor solution. Specifically, weigh 232.8 mg FAI (iodine formamide), 7.98 mg MABr (methylammonium bromide), 19.49 mg CsI (cesium iodide), 27.53 mg PbBr2 (lead bromide), 676.6 mg PbI2 (lead iodide) and 30.38 mg MACl (methylammonium chloride) and place them in a mixing container, add 1 mL of a mixed solvent of DMF and DMSO (wherein the volume ratio of DMF to DMSO is 4:1) to the mixing container containing the above raw materials, add diethyl methyl phosphonoacetate to the mixing container at a volume ratio of 0.5%:1 to mix, and obtain a mixed solution.

[0057] Step 4: Take 100 μL of the precursor solution and apply it on the hole transport layer. First, spin coat it at a speed of 2000 rpm for 10 seconds, then spin coat it at a speed of 5000 for 40 seconds to form a liquid film. Take 200 μL of chlorobenzene as an anti-solvent and spin coat it on the liquid film for 15 seconds. Then, anneal the perovskite film at 100°C on a hot stage for 30 minutes to form a perovskite light-absorbing layer with a thickness of 400 nm.

[0058] Step 5: Prepare the electron transport layer C on the perovskite light absorbing layer in sequence by vacuum evaporation method 60 The thickness of the BCP layer and buffer layer are 40nm and 5nm respectively.

[0059] Step 5: Prepare a metal electrode on the BCP layer using a vacuum evaporation method with a thickness of 100 nm to obtain a solar cell.

[0060] Example 2

[0061] The only difference from Example 1 is that in step 3, diethyl methyl phosphonoacetate is added into a mixing container for mixing at a volume ratio of diethyl methyl phosphonoacetate to the mixed solvent of 1%:1.

[0062] Example 3

[0063] The only difference from Example 1 is that in step 3, diethyl methyl phosphonoacetate is added into a mixing container for mixing at a volume ratio of diethyl methyl phosphonoacetate to the mixed solvent of 5%:1.

[0064] Example 4

[0065] The only difference from Example 1 is that the additive diethyl methyl phosphonoacetate in step 3 is replaced by triethyl phosphonoacetate.

[0066] Comparative Example 1

[0067] The only difference from Example 1 is that in step 3, the additive diethyl methyl phosphonoacetate is not added.

[0068] The perovskite solar cells prepared in the embodiment and the comparative example were respectively subjected to performance tests, and their photoelectric conversion efficiency (PCE), fill factor (FF), open circuit voltage (Voc) and short circuit current (Jsc) are shown in Table 1, respectively.

[0069] Table 1

[0070] Voc(V) <![CDATA[Jsc(mA / cm 2 )]]> FF(%) PCE(%) Example 1 1.128 25.74 85.35 24.80 Example 2 1.139 25.64 85.25 24.91 Example 3 1.142 25.78 83.85 24.70 Example 4 1.124 25.86 84.27 24.51 Comparative Example 1 1.122 25.29 83.66 23.74

[0071] It can be seen from Table 1 that the perovskite film prepared by the method for preparing the perovskite film according to the embodiment of the present invention is used as a light absorption layer of a solar cell, and the obtained perovskite solar cell has a high open circuit voltage, short circuit current density and fill factor, and a high photoelectric conversion efficiency.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a perovskite film, characterized in that: The steps include: Step S1, preparing a mixed solution including a perovskite precursor solution and an additive; Step S2, coating the mixed solution on a substrate to form a liquid film, and sequentially performing anti-solvent treatment and annealing treatment on the liquid film to obtain a perovskite film; Wherein, the perovskite film is an ABX3 type organic-inorganic hybrid perovskite film; the perovskite precursor solution contains organic cations, lead ions and halide ions that form the ABX3 type organic-inorganic hybrid perovskite film, and the organic cations are selected from methylamine ions and / or formamidine ions; The additive structure has a phosphono group and an ester group.

2. The method for preparing a perovskite thin film according to claim 1, characterized in that: The additive is a phosphonoacetate compound; Preferably, the additive is selected from one or more of diethyl methyl phosphonoacetate, triethyl phosphonoacetate, and trimethyl phosphonoacetate.

3. The method for preparing a perovskite thin film according to claim 1 or 2, characterized in that: The volume ratio of the additive to the perovskite precursor solution is (0.1% to 10%): 1; Preferably, the volume ratio of the additive to the perovskite precursor solution is (0.5% to 5%):

1.

4. The method for preparing a perovskite thin film according to claim 3, characterized in that: Calculated in terms of ABX3, the concentration of the perovskite precursor solution is 0.5 mol / L to 2 mol / L.

5. The method for preparing a perovskite thin film according to claim 1 or 2, characterized in that: The solvent in the perovskite precursor solution is selected from one of N,N-dimethylformamide and dimethyl sulfoxide or a mixture of the two in any proportion; Preferably, the solvent in the perovskite precursor solution is a mixed solvent formed by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (1-4):(1-2).

6. The method for preparing a perovskite thin film according to claim 1 or 2, characterized in that: In the step S2, the mixed liquid is coated on the substrate by spin coating to form the liquid film; Preferably, the spin coating rotation speed is 2000 rpm to 6000 rpm, and the spin coating time is 5 s to 50 s.

7. The method for preparing a perovskite thin film according to claim 1 or 2, characterized in that: In the anti-solvent treatment, the anti-solvent is selected from one or more of toluene, chlorobenzene, cyclohexane, and ethyl acetate.

8. The method for preparing a perovskite thin film according to claim 1 or 2, characterized in that: In the annealing treatment, the annealing temperature is 100° C. to 300° C., and the annealing time is 5 min to 60 min.

9. A perovskite film, characterized in that: The perovskite film is prepared according to the method for preparing the perovskite film according to any one of claims 1 to 8.

10. A solar cell comprising a light absorbing layer, characterized in that: The light absorbing layer comprises the perovskite thin film according to claim 9.

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