Preparation method for inducing phase change of perovskite crystal through organic solvent

Abstract

The invention belongs to the field of preparation of perovskite materials, and relates to a preparation method for inducing phase change of perovskite crystals by an organic solvent. The invention provides a perovskite crystal phase change method which comprises the following steps: heating, mixing and stirring cesium carbonate, lead acetate trihydrate, hydrobromic acid and 1, 6-hexamethylenediamine, and cooling to obtain a two-dimensional (HDA) CsPb2Br7 perovskite crystal; (HDA) CsPb2Br7 is cleaned by using an organic cleaning agent, dried and dissolved in an organic solvent to obtain a precursor liquid 1, and reverse extraction is performed in the precursor liquid 1 by using an anti-solvent to obtain the three-dimensional CsPbBr3 perovskite crystal. Adding haloid acid into the precursor liquid 1 to obtain a precursor liquid 2, and adding an anti-solvent into the precursor liquid 2 for reverse extraction to obtain the 0-dimensional Cs4PbBr6 perovskite crystal. According to the perovskite crystal conversion method, the phase change of the perovskite crystal can be realized through simple dissolution and recrystallization, and a new technology is provided for forming a heterojunction structure in a perovskite thin film material by using a surface modification technology.

Description

Technical Field

[0001] The present invention relates to the field of perovskite material preparation, and in particular to a method for preparing perovskite crystal phase change induced by an organic solvent. Background Art

[0002] Two-dimensional perovskites are widely used in optoelectronic fields such as photodetection due to their high absorption coefficient and flexible reconfigurability. However, the layered structure of two-dimensional materials severely limits the migration of charge carriers inside them, resulting in low efficiency of photodetectors. To solve this problem, constructing a heterojunction structure inside the perovskite material to improve the separation and extraction efficiency of photogenerated carriers and reduce the recombination loss of carriers is one of the common technologies currently used to improve carrier mobility.

[0003] Heterostructures commonly used in photodetectors generally include: heterojunctions of perovskites of different dimensions, heterojunctions of perovskites and traditional semiconductor materials, and heterojunctions of perovskites / low-dimensional materials. However, in multilayer heterojunction structures, defects such as interface amorphous layers, stress, and voids are common at their interfaces. These defects significantly increase phonon scattering in the interface region, affect the transmission and reflection behavior of carriers, and thus reduce device performance. In addition, when constructing heterostructures, the thickness and chemical composition of different functional layers have a great influence on the device, especially two-dimensional perovskites, which makes layer control and heterojunction formation more difficult. Surface modification technology can improve and enhance the surface properties of materials by changing the chemical composition and structural state of the materials. It can be applied to perovskite heterojunction structures to reduce interface defects. Patent CN202210950410.7 can achieve the preparation of top-down 2D / 3D heterojunctions, passivate buried interface defects, and promote carrier extraction and transmission by introducing specific organic ammonium salt molecules into the precursor liquid. However, the introduction of organic ammonium salt molecules may lead to ion contamination and, in some cases, the risk of causing degradation of perovskite materials. Compared with ammonium salt molecules, organic solvents can achieve the preparation of heterojunction structures by affecting the formation of perovskite crystals, avoiding the introduction of ion contamination and material degradation failure.

[0004] Therefore, it is necessary to provide a technology that induces perovskite crystal phase change through organic solvents, which can simply and effectively modify perovskite thin film materials and realize the preparation of uniform and controllable multi-dimensional perovskite heterojunction structure thin film materials. Summary of the invention

[0005] The object of the present invention is to provide a preparation method for organic solvent-induced perovskite crystal phase transition, wherein the preparation method can achieve the phase transition of two-dimensional perovskite to three-dimensional / zero-dimensional perovskite crystal by dissolution and recrystallization.

[0006] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0007] Cesium carbonate, lead acetate trihydrate and hydrobromic acid are mixed and stirred to dissolve to obtain a mixed solution.

[0008] Add 1,6-hexanediamine into the above-mentioned mixed solution, heat and stir, cool and precipitate, and obtain (HDA)CsPb2Br7 crystals.

[0009] The (HDA) CsPb2Br7 precipitate is cleaned with an organic cleaning agent until the solution is clear, an organic solvent is added and stirred until dissolved to obtain a precursor liquid 1, and then an anti-solvent is used for stripping to obtain CsPbBr3 crystals; hydrohalic acid is added to the precursor liquid 1 and stirred to obtain a precursor liquid 2, and then an anti-solvent is used for stripping to obtain Cs4PbBr6 crystals.

[0010] The molar ratio of cesium carbonate, lead acetate trihydrate and 1,6-hexanediamine is 1:(1-3):(1-3).

[0011] Wherein, the organic cleaning agent includes one or more of ethanol, acetone, isopropanol and ether.

[0012] Wherein, the organic solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, bromobenzene and chlorobenzene.

[0013] Wherein, the anti-solvent includes one or more of chlorobenzene, toluene, ethyl acetate, and trifluoromethylbenzene.

[0014] Wherein, the hydrobromic acid includes one or more of HBr, HCl, and HI.

[0015] Wherein, the volume ratio of the organic solvent to the anti-solvent is 1:(0.5~3).

[0016] Wherein, the stirring speed is 600-1000 rpm, and the stirring time is 15-90 min.

[0017] Wherein, the reaction temperature after adding 1,6-hexanediamine to the mixed solution is 60-120° C., and the cooling rate is 1-5° C. / min.

[0018] After the two-dimensional perovskite crystals described in the present invention are dissolved in an organic solvent, they coordinate with the solvent molecules to generate a variety of solvent compounds. After the anti-solvent is added, the solubility of the solution decreases rapidly, and the solute ions in the solution begin to autonomously form inorganic perovskite nuclei and grow into crystals at room temperature. The different chemical environments of the ions result in different coordination compounds formed by the ions, thus realizing the transformation of the two-dimensional perovskite crystals into different perovskite crystal forms.

[0019] Compared with the prior art, the preparation method of the present invention has the following advantages:

[0020] 1) The preparation method of the present invention is simple and convenient to operate, and has simple process requirements.

[0021] 2) The present invention can achieve a controllable transformation of two-dimensional perovskite to three-dimensional / zero-dimensional perovskite crystals by adjusting the solution environment in which the crystal is located.

[0022] 3) The present invention solves the problem of complex process requirements for perovskite crystal phase change, and can achieve direct transformation of perovskite crystals through simple crystal dissolution and stripping, which can simplify the preparation process of photodetector thin film materials and improve material uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the X-ray diffraction pattern of the (HDA)CsPb2Br7 perovskite crystal.

[0024] Figure 2 is an X-ray diffraction pattern of the CsPbBr3 perovskite crystal.

[0025] Figure 3 This is an X-ray diffraction pattern of the Cs4PbBr6 perovskite crystal. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0028] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0029] Embodiment 1:

[0030] 0.2 mmol Cs 2 CO 3 and 0.4 mmol Pb (CH 3 COO) 2·3H 2 O were added into 16 ml HBr, and stirred with a magnetic stirrer at room temperature with a stirring speed of 700 rpm for 30 min to obtain a mixed solution.

[0031] 2 mmol 1,6-hexanediamine was added to the mixed solution, stirred in a magnetic stirrer at 80°C with a stirring speed of 700 rpm for 60 min, and then the solution was cooled and crystallized at a cooling rate of 1°C / min. After cooling to room temperature, the supernatant was sucked out with a pipette, and the precipitate was repeatedly washed with ethanol and dried to obtain yellow precipitate (HDA) CsPb2Br7 crystals.

[0032] Attached Figure 1Shown is the XRD diffraction pattern of (HDA)CsPb2Br7. The powder diffraction peaks of this sample are a series of independent narrow peaks, indicating that the sample has good crystallinity.

[0033] Embodiment 2:

[0034] Take the above 0.5g (HDA) CsPb2Br7 yellow precipitate and add it to 6ml N,N-dimethylformamide, stir it with a magnetic stirrer at room temperature, the stirring speed is 300rpm, and the time is 30min, to obtain precursor liquid 1. Add 6ml toluene to the precursor liquid, stir it with a magnetic stirrer at room temperature, the stirring speed is 300rpm, and the time is 30min. Obtain yellow precipitate CsPbBr3.

[0035] Attached Figure 2 The figure shows the XRD diffraction pattern of the CsPbBr3 sample. The powder diffraction peaks of this sample are a series of independent, obvious narrow peaks, which match well with the standard card pattern in the PDF card library, indicating that the (HDA) CsPb2Br7 sample transforms into a three-dimensional perovskite CsPbBr3 under the induction of organic solvents.

[0036] Take the above 0.5g (HDA) CsPb2Br7 yellow precipitate and add it to 6ml N,N-dimethylformamide, stir it with a magnetic stirrer at room temperature, the stirring speed is 300rpm, and the time is 30min to obtain precursor liquid 1. Add 2ml hydrobromic acid to precursor liquid 1, stir it with a magnetic stirrer at room temperature, the stirring speed is 300rpm, and the time is 30min. Obtain precursor liquid 2. After adding 6ml toluene to precursor liquid 2, stir it with a magnetic stirrer at room temperature, the stirring speed is 300rpm, and the time is 30min to obtain green precipitate Cs4PbBr6.

[0037] Attached Figure 3 The figure shows the XRD diffraction pattern of the Cs4PbBr6 sample. The powder diffraction peaks of this sample are a series of independent and obvious narrow peaks, which match well with the standard card pattern in the PDF card library, indicating that the (HDA) CsPb2Br7 sample transforms into the zero-dimensional perovskite Cs4PbBr6 under the induction of organic solvents.

Claims

1. A method for preparing a perovskite crystal phase transition induced by an organic solvent, characterized in that: The following steps are involved: Cesium carbonate, lead acetate trihydrate and hydrobromic acid are mixed and stirred until dissolved to obtain a mixed solution; 1,6-hexanediamine is added to the mixed solution, heated and stirred, and cooled to obtain a precipitate (HDA) CsPb2Br7 crystal; the above (HDA) CsPb2Br7 crystal is cleaned and dried with an organic detergent, and then an organic solvent is added to dissolve to obtain a precursor liquid 1; an anti-solvent is added to the above precursor liquid and stirred to obtain a CsPbBr3 precipitate. Hydrohalic acid is added to the precursor liquid 1 to obtain a precursor liquid 2, and an anti-solvent is added to the precursor liquid 2 for stripping to obtain Cs4PbBr6 crystals.

2. The preparation method according to claim 1, characterized in that: The molar ratio of cesium carbonate, lead acetate trihydrate and 1,6-hexanediamine is 1:(1-3):(1-3).

3. The preparation method according to claim 1, characterized in that: The organic cleaning agent includes one or more of ethanol, acetone, isopropanol and ether.

4. The preparation method according to claim 1, characterized in that: The organic solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, bromobenzene and chlorobenzene.

5. The preparation method according to claim 1, characterized in that: The anti-solvent includes one or more of chlorobenzene, toluene, ethyl acetate, and trifluoromethylbenzene.

6. The preparation method according to claim 1, characterized in that: The volume ratio of the organic solvent to the anti-solvent is 1:(0.5-3).

7. The preparation method according to claim 1, characterized in that: The hydrohalic acid is one or more of HBr, HCl and HI.

8. The preparation method according to claim 1, characterized in that: The stirring speed is 300-800 rpm, the stirring time is 15-90 min, the temperature is 20-90° C., and the cooling rate is 1-5° C. / min.

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