Two-dimensional perovskite single crystal material and preparation method and application thereof

Abstract

The invention discloses a two-dimensional perovskite single crystal material as well as a preparation method and application thereof. The preparation method of the two-dimensional perovskite single crystal material comprises the following steps: dissolving lead iodide in hydroiodic acid to obtain a lead iodide solution; a C5 hydrocarbon compound is added into the lead iodide solution and fully dissolved, a mixed solution is obtained, and the C5 hydrocarbon compound is at least one of n-pentane, isopentane and cyclopentane; evaporating the mixed solution until the mixed solution is saturated, and then carrying out cooling crystallization, washing and drying to obtain the two-dimensional perovskite single crystal material. Through a steric hindrance engineering strategy, the precise regulation and control of the two-dimensional perovskite multi-exciton recombination rate is realized on the molecular scale, the unique advantages of high precision, high stability and low process complexity are shown, the important scientific value is achieved, and the huge industrialization potential is also shown.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic devices, and particularly relates to a two-dimensional perovskite single crystal material, a preparation method thereof, and an application thereof. Background Art

[0002] Organic-inorganic hybrid two-dimensional and quasi-two-dimensional perovskite materials are regarded as a new generation of semiconductor materials with great application potential due to their unique multi-quantum well structure, large absorption cross-section, and good environmental stability, etc., and have shown excellent performance in optoelectronic and photovoltaic devices such as solar cells, LED light-emitting devices, and lasers. On the one hand, the strong confinement effect inside two-dimensional perovskites can increase the binding energy of photo-generated electron-hole pairs and promote the recombination of photo-generated carriers, which is beneficial to improving the quantum efficiency; however, on the other hand, this also reduces the threshold for the occurrence of multi-exciton recombination processes, making the influence of non-radiative processes represented by Auger recombination on two-dimensional perovskite materials significantly stronger than that on bulk materials.

[0003] At present, Auger recombination inside two-dimensional perovskites usually occurs in the picosecond range, which is comparable to the radiative recombination and migration rates of carriers. This extremely fast Auger recombination seriously hinders the effective utilization of internal carriers and limits its future application potential. In recent years, through means such as chemical doping, interface engineering, and bandgap modification, people have achieved effective regulation of multi-exciton processes inside two-dimensional perovskites, and to a certain extent, extended the exciton lifetime and improved the efficiency of related devices. However, these methods still have many deficiencies, such as easy introduction of defect states, high process costs, strict material requirements, and complex synthesis processes, etc. Therefore, developing simple and effective strategies to regulate the multi-exciton recombination process inside two-dimensional perovskites while balancing the requirements in aspects such as material stability, regulation accuracy, and process complexity is crucial for promoting its applications in fields such as solar cells and light-emitting devices. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a two-dimensional perovskite single crystal material, a preparation method thereof, and an application thereof, so as to solve the problems of introducing defect states and high process costs during the multi-exciton regulation process in the prior art.

[0005] The purpose of the present invention is achieved through the following technical solutions: A preparation method of a two-dimensional perovskite single crystal material, comprising the following steps: Dissolve lead iodide in hydroiodic acid to obtain a lead iodide solution; Add a C5 hydrocarbon compound to the lead iodide solution and dissolve it fully to obtain a mixed solution, and the C5 hydrocarbon compound is at least one of n-pentane, isopentane, and cyclopentane; Evaporate the mixed solution to saturation, and then obtain the two-dimensional perovskite single crystal material after cooling crystallization, washing, and drying.

[0006] Preferably, the dosage ratio of lead iodide to hydroiodic acid is 0.06 - 0.4 mmol: 3 - 10 mL. More preferably, in some embodiments, the dosage ratio of lead iodide to hydroiodic acid is 0.13 - 0.394 mmol: 4 - 5 mL.

[0007] Preferably, the concentration of hydroiodic acid is 55%.

[0008] Preferably, in the step of adding C5 hydrocarbon compounds to the lead iodide solution, the molar ratio of C5 hydrocarbon compounds to lead iodide is 0.08 - 0.8: 0.06 - 0.4. More preferably, in some embodiments, the molar ratio of C5 hydrocarbon compounds to lead iodide is 0.16 - 0.776: 0.13 - 0.394.

[0009] Preferably, the step of adding C5 hydrocarbon compounds to the lead iodide solution and fully dissolving it specifically includes: adding C5 hydrocarbon compounds to the lead iodide solution and stirring at 90 - 120 °C for 20 - 30 min.

[0010] Preferably, the evaporation is isothermal evaporation, and the temperature of isothermal evaporation is 60 - 90 °C.

[0011] Preferably, the cooling rate is 10 - 20 °C / h.

[0012] Preferably, the washing is carried out with anhydrous ether, and the drying is carried out by vacuum drying. The temperature of vacuum drying is 40 - 60 °C. More preferably, in some embodiments, the temperature of vacuum drying is 70 °C.

[0013] A two-dimensional perovskite single crystal material, which is prepared by the preparation method of the above two-dimensional perovskite single crystal material.

[0014] The application of the above two-dimensional perovskite single crystal material in optoelectronic and photovoltaic devices such as solar cells, LEDs, and lasers.

[0015] The mechanism involved in the present invention: The present invention controls a single variable by fixing the inorganic layer structure and only changing the organic layer structure to exclude the interference of other factors, so as to focus on the study of the influence of the organic layer on the coupling strength. The main components of the inorganic layer are lead (Pb) and halogen (I), and its structure is formed by a layered framework in which PbI6 octahedrons are connected by sharing vertices. The coupling degree between the organic layer and the inorganic layer in two-dimensional perovskites significantly affects the multi-exciton recombination process, and organic molecules with different spatial configurations (C5 hydrocarbon compounds are used in the present invention) will change the distance and hydrogen bond strength between them and the inorganic layer. The present invention modifies the molecular structure of C5 hydrocarbon compounds through isomerization, ring formation, etc., and can accurately regulate the multi-exciton recombination rate, thereby optimizing the lifetime of photo-generated carriers and meeting the different requirements of different optoelectronic devices.

[0016] The C5 hydrocarbon compounds in the present invention are n-pentane, isopentane and cyclopentane. Selecting these three organic molecules has dual advantages: First, the synthesis process is mature and the cost is low, and it is easier to prepare on a large scale compared with the complex organic molecules reported in the literature; Second, their structures are simple, which can eliminate the interference of other adverse factors as much as possible except for steric hindrance, and accurately achieve single-variable regulation.

[0017] Compared with the prior art, the beneficial effects of the present invention include: The present invention realizes the regulation of the multi-exciton recombination rate inside the two-dimensional perovskite material at the molecular level by changing the steric hindrance. Compared with traditional macroscopic (or mesoscopic) methods such as doping and interface modification, the present invention can more accurately and directionally regulate, and has higher selectivity, which can effectively avoid introducing non-target effects. In addition, compared with technologies such as coating and band engineering, the present invention reduces the process complexity, does not require additional post-treatment and multi-step synthesis processes, and reduces the change and damage to the crystal structure. While realizing the directional regulation of exciton behavior, it can also optimize the carrier mobility and crystal stability. Therefore, the present invention shows unique advantages with its high precision, high stability and low process complexity, not only has important scientific value, but also shows great industrialization potential. Description of the Drawings

[0018] Figure 1 X-ray powder diffraction spectra of the two-dimensional perovskite single crystal materials prepared in Examples 1 to 3.

[0019] Figure 2 Scanning electron microscope photographs of (PA)2PbI4, (iPA)2PbI4 and (CPA)2PbI4 prepared in Examples 1 to 3.

[0020] Figure 3 Steady-state absorption spectra of (PA)2PbI4, (iPA)2PbI4 and (CPA)2PbI4 prepared in Examples 1 to 3.

[0021] Figure 4 Steady-state emission spectra of (PA)2PbI4, (iPA)2PbI4 and (CPA)2PbI4 prepared in Examples 1 to 3.

[0022] Figure 5 Kinetic statistical charts of Auger recombination of (PA)2PbI4, (iPA)2PbI4 and (CPA)2PbI4 prepared in Examples 1 to 3.

[0023] Figure 6Kinetic statistical graphs of Auger recombination for 2-(PA)2PbI4, 2-(iPA)2PbI4, and 2-(CPA)2PbI4. Detailed implementation mode

[0024] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Example 1 A method for preparing a two-dimensional perovskite single crystal material, the specific steps are as follows: (1) Take 0.13 mmol of PbI2 powder and dissolve it in 5 mL of hydroiodic acid with a concentration of 55% to obtain a clear lead iodide solution; (2) Add 0.16 mmol of n-pentylamine (PA) to the lead iodide solution obtained in step (1), heat it to 100 °C under magnetic stirring and maintain it for 30 min until the n-pentylamine is completely dissolved to obtain a yellow transparent solution; (3) Cool the yellow transparent solution described in step (2) to 70 °C, and then keep it at 70 °C and evaporate it at a constant temperature until the solution is saturated to precipitate fine crystals; then cool the saturated solution to room temperature at a rate of 20 °C / h to precipitate yellow crystals; filter and separate to obtain the yellow crystals, wash them three times with anhydrous ether, and finally dry them under a vacuum atmosphere at 70 °C to obtain the two-dimensional perovskite single crystal material.

[0026] The two-dimensional perovskite single crystal material prepared in Example 1 has a layered structure with alternating organic layers and inorganic layers; among them, the inorganic layer is composed of PbI6 octahedra linked by common vertices, the organic layer is composed of n-pentylamine, the organic molecules are connected by van der Waals forces, and the organic layer and the inorganic layer are connected by hydrogen bonds; the final product appears as yellow flaky crystals and emits green fluorescence under laser irradiation with a wavelength less than 450 nm. This two-dimensional perovskite single crystal material is represented by (PA)2PbI4.

[0027] Example 2 A method for preparing a two-dimensional perovskite single crystal material, the specific steps are as follows: (1) Take 0.13 mmol of PbI2 powder and dissolve it in 5 mL of hydroiodic acid with a concentration of 55% to obtain a clear lead iodide solution; (2) Add 0.16 mmol of isopentylamine (iPA) to the lead iodide solution obtained in step (1), heat it to 100 °C under magnetic stirring and maintain it for 30 min until the n-pentylamine is completely dissolved to obtain a yellow transparent solution; (3) Cool the yellow transparent solution described in step (2) to 70 °C, and then keep it at 70 °C for constant-temperature evaporation until the solution is saturated to precipitate fine crystals; then cool the saturated solution to room temperature at a rate of 20 °C / h to precipitate yellow crystals; filter and separate to obtain the yellow crystals, wash them three times with anhydrous ether, and finally dry them under a vacuum atmosphere at 70 °C to obtain the two-dimensional perovskite single-crystal material.

[0028] The organic layer of the two-dimensional perovskite single-crystal material prepared in Example 2 is isoamylamine, and the product appearance is yellow flaky crystals, denoted as (iPA)2PbI4.

[0029] Example 3 A method for preparing a two-dimensional perovskite single-crystal material, the specific steps are as follows: (1) Take 0.394 mmol of PbI2 powder and dissolve it in 4 mL of hydroiodic acid with a concentration of 55% to obtain a clear lead iodide solution; (2) Add 0.776 mmol of cyclopentylamine (CPA) to the lead iodide solution obtained in step (1), heat it to 110 °C under magnetic stirring and keep it for 20 min until the cyclopentylamine is completely dissolved to obtain a yellow transparent solution; (3) Cool the yellow transparent solution described in step (2) to 90 °C, and then keep it at 90 °C for constant-temperature evaporation until the solution is saturated to precipitate fine crystals; then cool the saturated solution to room temperature at a rate of 20 °C / h to precipitate yellow crystals; filter and separate to obtain the yellow crystals, wash them three times with anhydrous ether, and finally dry them under a vacuum atmosphere at 70 °C to obtain the two-dimensional perovskite single-crystal material.

[0030] The two-dimensional perovskite single-crystal material prepared in Example 3 has a layered structure with alternating organic layers and inorganic layers; among them, the inorganic layer is composed of PbI6 octahedrons linked by common vertices, the organic layer is composed of cyclopentylamine, the organic molecules are connected by van der Waals forces, and the organic layer and the inorganic layer are connected by hydrogen bonds; the final product appearance is orange-yellow flaky crystals, emitting green fluorescence under laser irradiation with a wavelength less than 450 nm, and this two-dimensional perovskite single-crystal material is denoted as (CPA)2PbI4.

[0031] In order to analyze the crystal structure of the prepared materials, X-ray powder diffraction was used to characterize the materials obtained in Examples 1 to 3, and the characterization results are as Figure 1 shown. From Figure 1From the results, it can be seen that characteristic diffraction peaks of perovskite appeared in all three crystals, and there were no impurity peaks interfering. The peak shapes were sharp, confirming the successful formation of perovskite single crystals and good crystallinity. At the same time, from CPA to iPA and then to PA, the 2θ corresponding to the X-ray diffraction peaks gradually increased (taking the diffraction peak around 20° as an example, from CPA to iPA and then to PA, 2θ changed from 20.1°→22.5°→24.4°), reflecting the influence of steric hindrance on the layer spacing of two-dimensional perovskite, that is, the interplanar spacing of two-dimensional perovskite with PA with small steric hindrance as the organic spacer layer was smaller.

[0032] To obtain the microscopic morphology of the prepared single crystal materials, scanning electron microscopy (SEM) was used to characterize the single crystal materials prepared in Examples 1 to 3, and the characterization results are as Figure 2 shown.

[0033] Figure 2 Figure shows the scanning electron microscope photos of (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3. From Figure 2 it can be clearly seen that all three crystals are flaky and have a multi-layer structure, confirming that the prepared single crystals are layered two-dimensional materials.

[0034] To compare the optical properties of the prepared single crystal materials, steady-state absorption spectra and steady-state emission spectra of the materials obtained in Examples 1 to 3 were tested using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, and the test results are as Figure 3 shown.

[0035] Figure 3 Figure shows the steady-state absorption spectra of (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3. From Figure 3 it can be seen that obvious exciton absorption peaks appeared in all three crystals at around 500 nm, reflecting strong interlayer coupling effects inside all three two-dimensional perovskites. At the same time, the wavelengths corresponding to the absorption edges of the three were not exactly the same, reflecting the regulation effect of organic molecules on the band-edge structure of two-dimensional perovskite single crystals.

[0036] Figure 4 Figure shows the steady-state emission spectra of (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3. From Figure 4 it can be seen that the fluorescence emission peaks of all three crystals are around 550 nm (excitation wavelength is 390 nm), but the peak shapes and peak positions are slightly different, indicating that while organic molecules regulate the optical properties of two-dimensional perovskite single crystals, they do not cause significant damage to their band structures.

[0037] The (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3 were tested using transient absorption spectroscopy to quantitatively characterize the multi-exciton recombination rate in the crystals. The characterization results are as Figure 5 shown.

[0038] Figure 5 Figure 6 is a kinetic statistical chart of Auger recombination of (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3. The dotted line in the figure is the original data, and the solid line is the result of fitting with a single exponential function. The time of Auger recombination can be obtained by fitting. From Figure 5 it can be seen that the Auger recombination times of the crystals with different organic ligands are different. The recombination times of PA, iPA, and CPA as organic ligands are 80 ps, 65 ps, and 70 ps, respectively. It can be seen that by changing the organic ligand, the Auger recombination time can be extended from 65 ps to 80 ps.

[0039] (PA)2PbI4, (iPA)2PbI4, and (CPA)2PbI4 prepared in Examples 1 to 3 were ground using an agate mortar (the same operator was selected to grind for 5 minutes each), and two-dimensional perovskite single crystals with smaller particle sizes were obtained, denoted as 2-(PA)2PbI4, 2-(iPA)2PbI4, and 2-(CPA)2PbI4, respectively. Under the condition of keeping the test conditions unchanged, transient absorption spectroscopy characterization was carried out on 2-(PA)2PbI4, 2-(iPA)2PbI4, and 2-(CPA)2PbI4 to compare the influence of crystal particle size on the multi-exciton recombination lifetime. The characterization results are as Figure 6 shown.

[0040] Figure 6 Figure 17 is a kinetic statistical chart of Auger recombination of 2-(PA)2PbI4, 2-(iPA)2PbI4, and 2-(CPA)2PbI4 under the same test conditions. The dotted line in the figure is the original data, and the solid line is the result of fitting with a single exponential function. The time of Auger recombination can be obtained by fitting. The Auger recombination times of the three crystals of 2-(PA)2PbI4, 2-(iPA)2PbI4, and 2-(CPA)2PbI4 obtained by fitting are maintained at 80 ps, 65 ps, and 70 ps, respectively, which are the same as those of the unground crystals, confirming that the crystal particle size has no influence on the Auger recombination time.

[0041] The specific embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A preparation method of a two-dimensional perovskite single crystal material, characterized in that, It includes the following steps: Dissolve lead iodide in hydroiodic acid to obtain a lead iodide solution; Add a C5 hydrocarbon compound to the lead iodide solution and fully dissolve it to obtain a mixture. The C5 hydrocarbon compound is at least one of n-pentane, isopentane, and cyclopentane; Evaporate the mixture to saturation, and then obtain the two-dimensional perovskite single crystal material after cooling crystallization, washing, and drying.

2. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, characterized in that, In the preparation step of the lead iodide solution, the dosage ratio of lead iodide to hydroiodic acid is 0.06 - 0.4 mmol: 3 - 10 mL.

3. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, wherein The concentration of the hydroiodic acid is 55%.

4. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, characterized in that, In the step of adding the C5 hydrocarbon compound to the lead iodide solution, the molar ratio of the C5 hydrocarbon compound to lead iodide is 0.08 - 0.8: 0.06 - 0.

4.

5. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, wherein The step of adding the C5 hydrocarbon compound to the lead iodide solution and fully dissolving it specifically includes: adding the C5 hydrocarbon compound to the lead iodide solution and stirring at 90 - 120 °C for 20 - 30 min.

6. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, wherein The evaporation is constant-temperature evaporation, and the temperature of the constant-temperature evaporation is 60 - 80 °C.

7. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, characterized in that, The rate of temperature decrease is 10 - 20 °C / h.

8. The preparation method of the two-dimensional perovskite single crystal material according to claim 1, characterized in that, The washing is carried out using anhydrous ether; the drying is carried out using vacuum drying, and the temperature of the vacuum drying is 40 - 60 °C.

9. A two-dimensional perovskite single crystal material, characterized in that, Prepared by the preparation method of the two-dimensional perovskite single crystal material according to any one of claims 1 - 8.

10. Application of the two-dimensional perovskite single crystal material according to claim 9 in solar cells, LEDs, and lasers.

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