Preparation And Properties Of Organic-Inorganic Hybrid Perovskite-like Crystals

Organic-inorganic hybrid halide perovskites,an important class of semiconductor materials with excellent low-temperature solution processability and band structure tunability,have been known for several decades.Recently,they have drawn great attention for applications in various types of optoelectronic devices,including photovoltaic cells,light emitting diodes,and photodetectors.Organic-inorganic hybrid halide perovskites are composite materials composed of organic ions and inorganic frameworks at molecular scale.As far as the structures of organic-inorganic hybrid halide perovskites are concerned,there are much less researches at present in two-dimensional（2D）structures comparing with well-studied three-dimensional（3D）structures.And the related reports of one-dimensional（1D）and zero-dimensional（0D）perovskite-like structures remain on the whole in the fields of synthesis and structural characterization.In this dissertation,the crystal growth,structure and properties of four organic lead（II）iodide perovskite-like crystals were studied.And these aspects,including the crystal growth method,the relationship between the structure and properties,the influence of the growth method on the properities,were discussed.The contents are as follows.Firstly,four organic-inorganic lead（II）iodide perovskite-like crystals were grown by several methods including hydrothermal method,antisolvent vapor-assisted crystallization（AVC）method and falling temperature method.These methods were also explored and discussed in this dissertation.Hydroiodide acid and sodium iodide solution were used in both the hydrothermal method and the falling temperature method,and three solvents and nine antisolvents were used in AVC method.Solvents include N,N-dimethyl formamide（DMF）,dimethyl sulfoxide（DMSO）,andγ-butylacyl（GBL）,and antisolvents include dichloromethane（DCM）,ethanol（CH₃CH₂OH）,acetone（（CH₃）₂C=O）,tetrahydrofuran（THF）,ethyl acetate（CH₃CH₂OOCCH₃）,acetonitrile（CH₃CN）,methanol（CH₃OH）,isopropanol（（CH₃）₂CHOH）),and toluene（C₆H₅CH₃）.Then,the chemical compositions of crystals were confirmed by thermogravimetric/differential thermal analysis（TG/DTA）,inductively coupled plasma-atomic emission spectrometry（ICP-AES）,scanning electron microscopy（SEM）with energy dispersive spectroscopy（EDS）and C-H-N elemental analysis.And their structure were preliminarily determined by X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FT-IR）.The high-quality crystals of trimethylammonium lead（II）iodide（TMAPbI₃）were analyzed by a single crystal diffractometer and refined by Shelxtl 6.10 software.Crystallographic analysis reveals that the crystal structure of TMAPbI₃ belongs to a trigonal system with the space group R3?（No.147）at room temperature,and the cell parameters were determined to be a=16.0514（3）?,b=16.0514（3）?,and c=72.280（2）?.Finally,the optical properties of crystals were tested by UV-visible diffuse reflectance absorption spectroscopy（UV-Vis）,photoluminescence spectroscopy（PL）,cathodoluminescence spectroscopy（CL）,and scanning electron microscopy（SEM）,and both the influence of synthesis methods on the crystal properties and the relationship between the structure and properties were discussed.It is hoped that this work can provide some references for the synthesis,design and application of such organic lead（II）iodide perovskite-like crystals.