Preparation And Performance Research Of All-inorganic Perovskite Luminescent Material Based On Surface Modification Strategy

All-inorganic perovskites(AIP)have become a star material with great development potential in the fields of display and lighting due to their excellent photoelectric properties,such as high photoluminescence quantum yield(PLQY),high color purity,rich emission colors and so on.However,in the development of AIP,there are some problems severely limiting the application of AIP in display,lighting and other fields,such as untunable emission color and poor luminescence performance of dual-color emission AIP,poor charge transport caused by organic surface ligands,and the unstable emission color of mixed-halogen AIP.Therefore,solving the above problems has great significance to the development of AIP.The research work is mainly elaborated from two aspects:(1)different kinds of surface ligands are introduced on the host lattice of AIP through surface modification to improve the photoelectric properties of AIP;(2)the material models are constructed by studying the action mechanism of surface ligands to form a systematic surface modification strategy.The specific research contents are as follows:(1)Aiming at the problem that the untunable emission color of dual-color emission AIP,the first example of ligand-induced dual-color emission AIP is prepared via using oligomers as surface ligands to modify the surface of host lattice.The mechanism of the surface ligand inducing the dual-color emission of the host lattice is discussed in detail through the characterization of the structural composition and photophysical properties of the AIP before and after the modification.This kind of ligand-induced dual-emission AIP can achieve rich emission colors in the visible light range.This work provides a new synthesis strategy for dual-color emission AIP,enriches the emission color of dual-color emission AIP,and promotes the development of dual-color emission AIP.(2)In order to solve the problem of poor luminescence performance of dual-color emission AIP,the post-synthesis surface modification strategy is used to introduce inorganic halides on the surface of the host lattice of the AIP to increase the PLQY to near-unity.For the surface lattice and internal lattice of ligand-induced dual-color emission AIP showing different emission,the ion distribution and mechanism of metal ions as surface ligands in the AIP are discussed in depth from the perspective of photophysical properties.The first example of dual-color electroluminescent device with a single luminescent layer is realized by using the dual-color emission AIP as the luminescent material.This work provides a new research idea for improving the luminescence performance of dual-color emission AIP,and greatly increases the application potential of AIP in the field of lighting display.(3)In order to break the problem of poor charge transport performance of traditional AIP,the surface of AIP is modified by adding s-triazine and its derivatives to prepare the AIP with excellent luminescence and charge transport properties.The effects of the triazine ring structure and the substituent groups on the triazine ring on the surface modification effect are analyzed and discussed through the characterization of the structure,luminescence,and charge transport properties of the AIP before and after the modification with different organic molecules.This work provides a new surface modification strategy for improving the charge transport performance of AIP,which is of great significance for improving the photoelectric properties of AIP.(4)In order to increase the stability of the emission color of the mixed halogen AIP,a series of blue-emitting AIP with stable emission color is synthesized by introducing organic cations on the surface of the mixed halogen AIP for surface modification.The influence of the composition of halogen in the host lattice and the content of-NH₃⁺in the organic ligand on the phase separation phenomenon of the material is summarized through the structural performance test of mixed halogen AIP with different halogen compositions before and after the surface modification.This work provides a systematic surface modification strategy for suppressing the phase separation phenomenon of mixed halogen AIP,and is of great significance for the design and synthesis of blue-emitting perovskite luminescent materials with stable emission colors.