Study On The Photoluminescence Kinetics Of Organic-Inorganic Hybrid Two-Dimensional Perovskites

In recent years,organic-inorganic hybrid two-dimensional perovskite materials have been developing rapidly,but their applications have been restricted by their photoluminescent regulation.In order to solve the problems of photoluminescence regulation,based on lead-based two-dimensional perovskites,we realized the efficient regulation of photoluminescence and kinetics from three aspects:bromine doping and defect passivation,halogen bond and chirality regulation,organic cation halogenation and bromine rich regulation.The main contents include:（1）In this work,a new and efficient solid-state photoluminescent perovskite system（PEA）₂Pb Br_xCl_4-x/Pb Cl₂（x=0,0.5,2,2.5,3,4;PEA=C₆H₅C₂H₄NH₃）has been synthesized for the first time through cooperative strategy of defect passivation and lattice distortion.The defect of two-dimensional perovskite is passivated by lead chloride at the grain boundary,which leads to the enhancement of its photoluminescence intensity and the prolongation of its photoluminescent lifetime.Moreover,the distortion of perovskite octahedral structure is reduced by the bromine doping,which leads to the tuning of the photoluminescent color of（PEA）₂Pb Br_xCl_4-x/Pb Cl₂from white to blue.The above results show that（PEA）₂Pb Br_xCl_4-x/Pb Cl₂ has potential applications in optoelectronic devices through the combination of interface engineering and crystal engineering.（2）In this work,a series of novel organic-inorganic hybrid two-dimensional chiral perovskite materials（R-X-p-m BZA）₂Pb Br₄（X=H,F,Cl,Br;m BZA=α-methylbenzylamine）,which include halogen bond,were synthesized for the first time by introducing halogenated chiral organic molecules such as fluorine,chlorine and bromine into the a position of perovskite.The halogen bond regulation strategy solves the problems of narrow emission,weak chirality and low fluorescence quantum yield of chiral perovskite.The emission spectrum of perovskite is greatly broadened due to the existence of both free exciton emission and self-trapped exciton emission.Via the halogenated bond fixation effect,the chirality of the A-site molecule was transferred from the A-site molecule to the whole perovskite and amplified.In addition,the fluorescence quantum yield has been improved,which is due to the reduction of energy gap and the forbidden of non-radiative transition.Therefore,the halogen bond regulation strategy of A-site cations provides a new way to regulate the photoelectric properties of two-dimensional chiral perovskites.（3）In this work,we have synthesized a series of organic cation halogenated perovskite materials（X-p-PEA）₂Pb X₄（X=Cl,Br;p:para-position;PEA=ethylammonium）.The organic cation halogenation strategy solves the long-life problems of white blue light emission control and organic-inorganic hybrid perovskite.At the same time,the fluorescence quantum yield of perovskite was improved by the bromine enrichment strategy.The competition between free exciton emission and self-trapping exciton emission is regulated by the halogenation of organic cations,which makes the photoluminescence of perovskite regulated.Moreover,the effect of rich bromine can be used to improve the fluorescence quantum yield by reducing the non-radiation deactivation.At the same time,the organic cation halogenation strategy significantly accelerates the excited state relaxation process,which shortens the lifetime of perovskites.Therefore,the halogenation strategy of A-site cations provides a new idea for the application of organic-inorganic hybrid two-dimensional perovskite in the field of optoelectronics.The development of the above works has regulated the photoluminescence dynamics of two-dimensional perovskite from the two aspects of interface engineering and crystal engineering,so as to regulate its optical properties.The three strategies of defect passivation and bromine doping,halogen bond and chirality control,organic cation halogenation and bromine rich control are put forward to realize the efficient regulation and promotion of the optical properties of perovskites,which opens a new way for the application of organic-inorganic hybrid perovskites in the field of optoelectronics.