The Structural And Optical Properties Of Zero-dimensional Double Perovskite Cs₂Zr_（1-x）Te_XCl₆ Under High Pressure

People’s demands for lighting infrastructure have become more stringent as people’s quality of life has improved,making it difficult for some light equipment on the market to keep up with the rising demand in recent years.We must create new light-emitting technologies that are stable,hygienic,and diversified.Due to their high absorption coefficients,controllable narrow-band emission,low cost of raw ingredients,and straightforward synthesis techniques,metal halide perovskites materials are regarded as suitable light-emitting diode materials for solid-state illumination and photoelectric sensing.The most representative metal halide perovskite,of special actual interest,is a lead-based halide perovskite-based LED device.Unfortunately,the performance of the optical devices made by lead-based halide perovskites is unstable due to their susceptibility to moisture and humidity in the environment.At the same time,lead element poisoning of the environment is a permanent issue.Researchers have suggested creating a new lead-free perovskite to address these issues.They have created a novel kind of perovskite,whose structural general formula is A₂B⁺B³⁺X₆,by substituting two lead ions with a+1 metal cation and a+3 metal cation.In addition,in order to further improve the luminescence properties of perovskites material,scientists have used ion doping to modulate the optical band gap of perovskites material.The doping technique,which refers to the addition of some trace elements to the original material,is used to modulate the underlying properties of the substance.However,it is found that it is difficult to precisely control the specific content of doping in the experiments,so it is very difficult to regulate the photoelectric properties of perovskites by only a single doping means.High pressure,as an efficient and clean means of regulating the fundamental properties of material,is of considerable interest.Pressure,without changing the composition of substance,causing a change in the fundamental properties of substance by compressing the distance between atoms,thus influencing the original crystal structure.Therefore,this thesis explores the relationship between optical changes and crystal structure of metal halide double perovskite by pressure on the basis of ion doping.The related research results fill the gap of metal halide double perovskite in the field of high pressure and provide some help for the subsequent research of lead-free perovskites.In this thesis,a zero-dimensional（0D）pure inorganic halide double perovskite Cs₂Zr Cl₆was chosen as the object of study,to investigate the relationship between the optical response behavior of Te ion-doped Cs₂Zr Cl₆crystals and the structural changes under high pressure.Revealing the optical behavior of Te ion-doped and Te ion-undoped Cs₂Zr Cl₆crystals by combining of in situ high pressure fluorescence,in situ high pressure UV-VIS absorption and in situ synchrotron X-ray diffraction test methods.It is shown that peculiar optical changes in Te ion-doped Cs₂Zr Cl₆crystals with pressure-induced emission enhancement in the low-pressure range.The extreme value of the structural distortion of[Te Cl₆]^2-octahedra just corresponds to the pressure point corresponding to the emission enhancement,again corroborating that the related emission enhancement of self-trapped exciton is due to the Jahn-Teller effect producing structural distortion of the octahedra of the luminescent group.The calculation of the first principles also provides a theoretical basis for the mechanism of pressure-induced emission enhancement of the self-trapped state luminescence.The related research results can provide some assistance in developing new material and it also expands the potential applications of pure inorganic halide double perovskite Cs₂Zr Cl₆in pressure switches,pressure sensing and optical pressure sensors.