Preparation And Chiral Properties Of Lead Halide Perovskite Single Crystals

Since the advent of perovskite-type materials,perovskite has occupied the top of the pyramid of materials due to its excellent characteristics such as adjustable band gap,high carrier mobility,and long carrier diffusion length,and because of its simple synthesis process,Low cost and other advantages have promoted the realization of large-scale production and industrial application of perovskite material devices.As a hot material for new types of solar cells,perovskite-based batteries have a trend to catch up with silicon-based batteries.The conversion efficiency of this battery is constantly setting new world records.During the rapid development of solar cells,it has soared from 3.8%to 25.5%,which shows the power of perovskite materials should not be underestimated.Compared with polycrystalline materials,perovskite single crystals have no grain boundaries,fewer defects,a wider spectral range,and higher absorption coefficients,making them widely used in photodetectors,high-energy ray detectors,display imaging,solar cells,etc.This thesis closely follows the research hotspots of materials,based on perovskite single crystal materials as the main body of research,with the synthesis of perovskite as the core research,and synthesizes low-dimensional perovskite single crystals through different methods,and further studies on perovskite single crystals.Expanded exploration of the properties of ore single crystals,including chirality and heterojunction.The specific innovations are as follows:1.From the perspective of geometry,perovskite single crystals can be divided into one-dimensional,two-dimensional and three-dimensional single crystals.One-dimensional and two-dimensional single crystals have the characteristics of anisotropy and low carrier recombination rate in light absorption,which makes them better than three-dimensional single crystals in special fields.This paper introduces the basic method of growing high-quality APbX₃ perovskite large single crystals.It is proposed to combine the fusion crystallization method with mechanical confinement to successfully grow the CsPbBr₃ quasi-one-dimensional single crystal encapsulated in a silica fiber capillary for the first time.This method can improve its stability Effectively by isolating water and oxygen.The diameter of CsPbBr₃ was adjustable from 20?m to100?m;through the combination of ITC method and the confinement,the perovskite single crystals with exposed(110)and(001)crystal faces are grown;supplemented by the surface treatment of the glass sheet,Thin slices of perovskite crystals with side length of 1 mm?2 mm are grown between the glass sheets;in addition,we propose for the first time that perovskite crystals are confined in the two-dimensional liquid film of bubbles,which provides a new idea for confined growth of low-dimensional perovskite crystals.2.Hybrid organic-inorganic perovskites(HOIPs)are important materials in optoelectronics for their outstanding physical and chemical properties If the HOIP crystal is given chirality,its application will be broadened to the fields of chiral optoelectronics,chiral spintronics,and nonlinear optics.To design a chiral HOIP,the basic idea is incorporating chiral cations into the A-site.However,due to the spatial limitation of the crystal structure and the difficulty of synthesis,HOIP single crystals with a chiral three-dimensional structure are still stuck in theoretical predictions.How to synthesize and purify these chiral molecules is still a huge challenge in experiments.In our study of growing chiral 3D HOIPs,we have found that theoretically achiral 3D structure MAPbBr₃ single crystal prepared by ITC method has optical activity at 300nm?455 nm and 455 nm?525 nm,and the wavelength range can be adjusted from365 nm to 470 nm by controlling the halogen components,which broadens its applicable wavelength range in the application of chiral single crystals.Experimental data and theoretical calculations show that MA⁺with different chiral orientations combines with the Pb-Br framework structurally and electronically to form a chiral supercell,which induces the chiral activity of the single crystal.This discovery provides a new idea for the preparation of chiral ligands/molecules/cation-free chiral materials.3.The properties of perovskite materials and the excellent device performance are not only derived from the intrinsic properties of perovskite materials,but also from the hybrid composite material system of perovskite and heterogeneous materials.The formation of perovskite heterojunction not only improves material stability,but also improves device performance.This article describes the synthesis of X?MAPbBr₃single crystal heterojunctions by the ITC method.X can be inorganic metal nanomaterials,inorganic non-metallic elements,metal oxides or metal sulfides,the blending concentration of C Dots can reach 40 mg/mL.This method has Universal potential.Based on the C Dots?MAPbBr₃ heterojunction single crystal grown by this method,we have completed the production of a photodetector prototype in the near-infrared region.The doping of carbon dots can help improve the photo responsibility of the perovskite crystal to the near-infrared region(?=1064 nm),this work provides a new direction for the detection of photodetectors based on perovskite single crystals in the near-infrared region.