Preparation And Properties Of Cs₃Cu₂Br₅ Perovskite-like Single Crystal Based On Self-trapped Exciton Luminescence

In recent years,perovskite materials have been widely used in solar cells,electroluminescent LEDs,photodetectors and other fields due to their excellent photoelectric properties,which has attracted the attention of a large number of researchers.However,the traditional perovskite materials still have some disadvantages.Firstly,the organic part of the organic-inorganic hybrid perovskite has poor stability,which is easy to decompose when meets heat and water.Secondly,the lead element of traditional perovskite materials has great toxicity and contamination,and the subsequent dispose of waste devices is more complex.Therefore,in order to promote the development and progress of perovskite materials in practical application,it is urgent to find a suitable element to replace the lead element in traditional lead based perovskite,we should keep its excellent photoelectric properties as much as possible while realizing the non-toxic of materials.In this paper,antisolvent method was used to prepare copper-based lead-free perovskite Cs₃Cu₂Br₅ single crystal material based on self-trapped exciton luminescence by using non-toxic copper element instead of lead element in the traditional lead based perovskite.Based on this,we carried out doping experiments of TFA^-and Bi³⁺ions,and tested and analyzed its structure and fluorescence properties.The research contents of this paper mainly include the following aspects:By adjusting the proportion of raw materials and the growth temperature,the growth conditions of the crystals were explored,the structure and fluorescence properties of the materials were characterized,analyzed and compared by single crystal X-ray diffraction,powder XRD and fluorescence spectrophotometer,the crystal structure of the material and the growth conditions for the maximum fluorescence intensity of the crystal were obtained.After the crystals was placed in atmospheric environment for 90 days,the PL intensity drops to 96.91%of the fresh crystals,thermogravimetric analysis show that the complete decomposition temperature of the powder is above 929?,the material has excellent stability.The fluorescence excitation spectra and variable temperature fluorescence of the prepared materials were analyzed,and it was found that the prepared materials had the spectral characteristics of self-trapped exciton emission like wide spectrum emission and large Stokes shift,theoretical calculations show that the material has a deformable lattice structure and the basic conditions for self-trapping exciton emission,the broad spectrum luminescence of the material is due to the self-trapping exciton emission.The structure and fluorescence properties of TFA^-and Bi³⁺ions doped materials were characterized,analyzed and compared.It was found that the XRD diffraction peaks have a blue shift compared with the undoped material,shows that the two ions were successfully doped into the lattice structure of the material.The fluorescence intensity is1.3 and 2.2 times higher than that of undoped materials,respectively,among which the improvement of quantum yield shows that TFA^-ion significantly improved the crystallinity of the materials.