Synthesis And Properties Of The Layered Perovskite Structures

Organic-inorganic hybrid layered perovskites have broad application prospects due to their outstanding photoelectric properties.At present,more researches focus on two-dimensional?2D?single-layer perovskites,and research on two-layer and multi-layer perovskites at home and abroad has also attracted widespread attention in recent years.2D perovskites are interrupted by the insertion of organic cations on crystal plane by three-dimensional?3D?structure,which may alter the stability and functionality of the material.This paper is divided into three parts.A series of two-dimensional single-layer and multi-layer perovskite compounds were synthesized by using some organic amine salts as templates,and the properties of these compounds were studied.The first part mainly studies the reversible phase transition and optical properties of a single-layer two-dimensional perovskite compound[?FBMA?₂PbBr₄]?FBMA=3-fluoro-N-methylbenzylamine?.The crystal[[FBMA)₂PbBr₄]was synthesized in a certain proportion by using 3-fluoro-N-methylbenzylamine and lead bromide in hydrobromic acid,and was found by differential scanning calorimetry?DSC?at a temperature of T=112°C.A reversible phase transition occurs,and it is further confirmed by the temperature-changing single crystal that the phase transition is caused by the ordered-disorder transition of the organic cation in the compound.In addition,it was confirmed by fluorescence spectroscopy that the compound had a strong fluorescence emission peak at 443 nm at an excitation wavelength of 380 nm.The second part mainly studies the synthesis of?TMA?₂?MA?Pb₂I₇ and?TMA?₂?FA?Pb₂I₇ with methylamine salt?MACl:CH₃NH₃Cl?and formazan salt?FACl:CH₅N₂Cl??TMA=2-thiophenemethylamine?.The crystal structure of two crystals at room temperature and high temperature was studied by single crystal diffractometer.The phase transition and dielectric properties of the two compounds was studied by differential scanning calorimetry?DSC?and dielectric test.The third part mainly introduces 4-fluorobenzylamine?4-FBA?as a large organic cation to synthesize a series of two-dimensional layered perovskites with the general formula:[?4-FBA?₂?MA?_n-1Pb_nI_3n+1]?4-FBA=4-FC₆H₄CH₂NH₃,MA=CH₃NH₃,n=1,2,3,n represents the number of inorganic compound layers?.The crystal structure can be seen as a multi-layered perovskite structure formed by cutting 3-fluorobenzylamine along a specific crystal plane to cut 3D[MAPbI₃].According to the UV-visible absorption,the band gap of the multilayer compound decreases as the number of inorganic perovskite layers increases?n=1,Eg=2.23 eV;n=2,Eg=2.01 eV;n=3,Eg=1.78 eV?,therefore the layered compound may have potential applications in solar absorption.