Study On The Fabrication And Properities Of Light-Emiting Organic-Metal Halides

Organic-inorganic hybrid perovskite（OIHP）,which is of virous structures and excellent optoelectronic properties,has a wide range of applications in the fields of solar cells,light-emitting diodes,photodetectors,lasers,scintillators and so on.The research and application of halide perovskites has become one of the hot areas of the interdiscipline between photoelectric functional materials and semiconductor materials.Among these materials,low-dimensional metal halide crystal materials have attracted extensive attention in recent years.Compared with traditional three-dimensional materials,some low-dimensional materials usually have better stability and more unique physical and chemical properties,and have good application prospects in the fields of information,micro/nano optoelectronics and so on.For low dimensional metal halide crystals,the selection of organic ligand molecules is of vital important for the synthesis of materials and the improvement of optical and electromagnetic properties.However,at present,the selection of organic ligand molecules is still in the stage of screening after a large number of randomized experiments,which greatly limits the exploration,design and development of low-dimensional organometallic halide materials,the study of structure-property relationship,as well as the further application in the field of photoelectric functional materials.In this work,we mainly focus on the enrichment of organic metal halide luminescent materials.In this work,we choose and introduce the gua-containing organic molecules as organic template molecules,which is a type of universal organic“host”molecule in molecular recognition,bonding chemistry as well as supramolecular chemistry,into the metal-halides frameworks to fabricate and expand the organic metal halides family because the molecules containing guanidine have multiple interaction sites,meanwhile,it can interact with one or more anions“guest”molecules.By regulating the hydrogen bonding and other non-bonding weak interactions between organic guanidine cations and between them and the inorganic metal halides framework,a series of organic metal halides photoelectric materials with various structures,multiple compositions and excellent photophysical properties have been successfully constructed,realizing photoluminescence and mechanoluminescence.The research results are mainly concentrated in the following three aspects:1、Construction of lead-based halide white light fluorescent materialsDistorted structure is designed through multiple hydrogen bond interactions to achieve wide spectrum fluorescence emission.First,we chose the organic molecule containing the functional group of guanidine as the organic cationic ligand and chose lead as the organometallic center to prepare the organic-inorganic hybrid lead halogen perovskite materials with two-dimensional layered structure.The prepared fluorescent crystals based on this principle have wide emission and large Stokes-shift.By adjusting the type and ratio of halogens and other conditions unchanged,the fluorescence emission range of organometallic halogen perovskite and its photophysical properties can be adjusted,and the emission from cold white light to warm white light can be realized.Based on the analysis of the single crystal structure of this newly prepared single crystal,we found that as the guanidine organic cationic have more than one interaction site after the protonation of guanidine,the electron delocalization,makes each N atoms within the organic molecules become potential interaction site,and the inorganic lead halide octahedral unit of halogen atoms anion through super molecular hydrogen bonding interactions.Compared with the traditional three-dimensional perovskite,the structure of the lead halogen skeleton inorganic octahedron here is greatly distorted,and the bond length and bond Angle are greatly offset.This twisted octahedral structure is due to the fact that organic guanidine molecules contain multiple ligands,which can interact with multiple Br.Abundant supramolecular interactions make the synthetic materials show distinct characteristics from traditional three-dimensional perovskite materials in terms of dimension and luminescence properties.2、Zero-dimensional guanidine-antimony compounds with high-efficiency fluorescence property.High steric hindrance gua-ligands are used to build highly efficient zero-dimensional fluorescent crystals.We select organic molecules containing guanidine functional groups as cations and introduce phenyl groups with high steric hindrance,which further reducing the material dimensions through steric hindrance effect.The selected cationic ligands are co-crystallized with antimony-based halides （gua-DPG）₃SbCl₆.Organometallic halides with zero-dimensional structure are successfully prepared,which shows high efficiency of orange-light emission,and the photoluminescence quantum yield（PLQY）is nearly approaching 100%.This work further indicates that gua-containg organic molecules can act as as organic template cations for fabricate organic-metal halides.3、Thirdly,we continue to use the organic molecules containing guanidine functional groups as a contrast cation to co-crystallize with manganese based halides,and successfully prepare a series of organo-metal halides（Bigua）_xMnBr₄（x=1or2）with zero-dimensional structure,which exhibit efficient green light emission,and the photoluminescence yield is as high as 60%.In this part,we constructed low-dimensional supramolecular crystals by changing the number of functional guanidine groups in organic molecules and providing hydrogen bond donors with different densities.Triboluminescence and photoluminescence of high-density hydrogen bond crystals and photoluminescence of low-density hydrogen bond crystals are successfully achieved.Our study proves that guanidine derivatives are very valuable molecules for the low dimensional template metal halide crystal,which provides a new idea for the synthesis of new low-dimensional crystal.Guanidine derivatives,which is on kind molecules of intramolecular hydrogen bond density of accurate control,can be successfully implemented to improve the performance of metal halide crystal and special photoelectric performance electroluminescent（force）the construction of the crystal so guanidine derivatives were used as template agent for building new organic metal halide light function material provides a new way.In a word,in this thesis we mainly intrudce gua-containing organic molecules into the inorganic metal-halides framworks,and successfully obtain a series of light-emitting organic metal halides with different metal centre.Further,by choosing appropriate guanidine molecules,we can regulate the interaction between the guanidine organic moiety and inorganic metal halides frameworks,and thus realize the regulation of the electro-optical properties.The research not only enriches the organic-inorganic hybrid metal-halides with luminescent,but also provides a new pathway for its design and synthesis.The work also helps us to understand the relationship between structure,properties and its application.This work will guide the further research on the construction of organic metal halides with luminescent properties.