Syntheses,Compositional Modulation And Characterization Of Two-dimensional Perovskites Modified By 5-Aminoisophthalic Acid

Two-dimensional(2D)perovskite is a typical representative of metal halide perovskite(ABX₃)split along a certain crystal plane.As a new type of material combining organic and inorganic molecules at the molecular level,2D perovskite can have the dual properties of organic and inorganic materials at the same time,which the unique property makes it have broad development potential in many fields.This article focuses on 5-aminoisophthalic acid(5APA)as the organic core unit,and selects a series of metal cations(Pb²⁺,Cd²⁺,Sn²⁺,Mn²⁺)to carry out research to realize the regulation and control of the structure and performance of perovskite,on this basis,study the structure morphology and optical properties of the material,expand its application potential in different fields.The main research contents are as follows:(1)Selecting 5-aminoisophthalic acid,2-aminoisophthalic acid,m-aminobenzoic acid and p-aminobenzoic acid as the organic layer,Cd Cl₂ as the inorganic layer,a series of 2D perovskites were prepared by the liquid phase method Among them,(5APA)₂Cd Cl₄ has a visible yellow-green room temperature phosphorescence emission,and its X-ray diffraction pattern(XRD)shows periodic diffraction,indicating its layered structure.Scanning electron microscopy(SEM)further confirms its layered structure and flakes.shaped stacked morphology.By characterizing the spectral properties of(5APA)₂Cd Cl₄,the sample exhibits phosphorescence emission at 515 nm under excitation at 266 nm.By comparing the PL spectrum of 5APA,the phosphorescence emission peak of the sample belongs to the triplet state(T₁)of 5APA,the fluorescence emission at 450 nm is attributed to the singlet(S₁)emission of 5APA.The reason for the obvious increase in phosphorescence is due to the energy transfer between the inorganic layer and the organic layer.The room temperature phosphorescence lifetime is 266 ms,and the phosphorescence quantum efficiency is 7.2%.(2)Based on 5APA as the organic layer,a series of 2D perovskite(5APA)₂MX₄(M=Pb²⁺,Sn²⁺,Cd²⁺;X=Br^-,Cl^-)was prepared by changing the composition of the inorganic layer.The morphology of its layered structure and sheet-like stack was confirmed by XRD and SEM.The perovskite based on the Br system has no room temperature phosphorescence emission,and the perovskite material based on the Cl system exhibits strong room temperature phosphorescence emission.The phosphorescence emission peaks of the samples are all located at about 520 nm,and the shape of the emission spectrum is similar,which indicates that the phosphorescence emission comes from the same luminescence center,the 5APA.The process also has energy transfer between the inorganic layer and the organic layer.The phosphorescence lifetime and phosphorescence quantum efficiency of(5APA)₂Pb Cl₄,(5APA)₂Sn Cl₄ and(5APA)₂Cd Cl₄ at 265 nm are 59.98 ms/2.4%,90.13 ms/4.2%and 266.05 ms/7.2%respectively.The difference in the results may be due to the difference in the packing density of the perovskite structure caused by the difference in the radius of the metal ions.The dense structure is beneficial to suppress the molecular vibration and improve the phosphorescence performance.(3)Prepare metal ion doped red light perovskite(5APA)₂Pb_xMn_1-xBr₄by introducing Mn²⁺,Through XRD and SEM characterization of the perovskites doped with different concentrations of Mn²⁺,the morphology and layered structure did not change.Further optical performance characterization results show that the red light emission at 605 nm is attributed to the d-d transition of Mn²⁺.When the doping concentration is 40%,the emission intensity reaches the maximum intensity,and the fluorescence quantum efficiency reaches 68%.At the same time,there is also energy transfer from the excitons in the conduction band of the inorganic layer to the energy level of the ⁴T₁ excited state of Mn²⁺.