Growth And Properties Of Halide Perovskite Composite KBr_1-xCl_x Crystals

There are lots of researches about alkali metal halide crystals in numerous fields,but research reports in the visible light field are relatively rare,lacking strategies for achieving visible light emission.Rare earth ion doping is a common approach to achieve visible light emission,but this strategy has the drawbacks of high cost and fixed emission band,which limits its practical application.In order to expand the application of alkali metal halide crystals in the visible field,the strategy of doping chalcogenide halide into KBr_1-xCl_xcrystals is proposed in this paper.A series of halide perovskite doped KBr_1-xCl_x crystals was grown by the Czochralski method,and the structure and optical properties of the crystals were investigated in depth.As follows:（1）The crystalline phase structures of CsPbBr₃ and KBr_1-xCl_x were comparatively analyzed.The crystal surface matching degree at 26.5°and 38.0°is calculated,which is98.23%and 98.94%,which theoretically verified the feasibility of the crystal growth of halide perovskite doped KBr_1-xCl_x.（2）The crystal components were designed and the polycrystalline material ratios of CsPbBr₃:KBr_1-xCl_x（1:50）were determined.Using the purified KBr and KCl as raw materials,CsPbBr₃:KBr_1-xCl_x crystals were grown by the Czochralski method with a sintering temperature of 700℃and a holding time of 7 min.A series of characterization and analysis of the structure,morphology and optical properties of the polycrystalline materials were carried out to compare the quality of the polycrystalline materials and to determine the factors affecting the quality of the polycrystalline materials.（3）The temperature field and process of CsPbBr₃:KBr_1-xCl_x（x=0,0.2,0.4,0.6,0.8,1.0）crystal growth were investigated.The furnace chamber is adjusted and optimized for temperature measurement,obtaining a more reasonable temperature field.The optimal radially centered and axially centered position of the crucible in the furnace chamber is determined by temperature field measurements.A series of CsPbBr₃:KBr_1-xCl_x（x=0,0.2,0.4,0.6,0.8,1.0）crystals were grown.（4）CsPbBr₃:KBr and CsPbBr₃:KBr_0.6Cl_0.4 crystals were selected for the characterization and analysis of structural,morphological and optical properties.The lattice constants of the crystals were obtained by XRD in accordance with the theoretical values,and the states of each element of CsPbBr₃ in the crystals were determined by the combination of XPS and HRTEM and other test analyses.The temperature dependence of the photoluminescence of the crystal was analyzed by variable temperature spectroscopy and fluorescence lifetime tests,and it was concluded that the broadening of the FWHM in the spectrum with increasing temperature is caused by temperature-induced longitudinal optical phonon scattering,and its thermal stability was explained by combining with related theories.