Research On Phase Transition Of All-inorganic Lead Halide Perovskite And Its Physical Properties Of Fluorescence

All inorganic lead halide perovskite due to its own ionic bonding properties resulting in its poor chemical stability,especially water stability,lead halide perovskite once contact with moisture in the external environment will rapidly disintegrate into non-perovskite phase,all kinds of excellent optoelectronic properties will be significantly reduced.On the other hand,the mixed lead halide perovskite used in solar cells will undergo phase transformation due to the photoluminescence process,and the uniformly composed lead halide perovskite will segregate into I-rich region or Br-rich region during the photoluminescence process,and the I-rich region will become a charge carrier trap,which has a great impact on the open circuit voltage and current extraction efficiency,so that the CsPbX₃ photostability problem in such devices also needs to be addressed.Thus,how to improve the water stability and photostability of lead halide perovskite in a simple and efficient way is a major research challenge to promote its commercial application,and there is an urgent need to find a solution with a simple process and wide application range.To this end,the following studies were conducted in this work:1、Ions are released from CsPbBr₃ semiconductor powder to design new hybrid halide semiconductor structures.A part of CsPbBr3 is transformed into Cs Pb₂Br₅ in water,and another part of CsPbBr₃ is transformed into CsPbBr₃ QDs in water to grow in situ into Cs Pb₂Br₅/Pb Br（OH）with high chemical stability,which significantly improves the water stability of lead halide perovskites and maintains the luminescence intensity in a stable state even in extreme environments such as acid and alkali.Finally,based on the linear relationship between fluorescence intensity and water concentration,a sensing model was developed for the quantitative detection of water concentration,paving the way for the realization of illumination and sensing of halide semiconductor QDs in water.2、The light-induced phase transition in the material was observed by a modified vapor deposition method to obtain the mixed halide perovskite Cs Pb Cl_1.2Br_1.8 grown on the substrate.Subsequently,the photostability of the mixed halide perovskite was improved and the light-induced phase transition effect in Cs Pb Cl_1.2Br_1.8 was effectively suppressed under the joint adjustment of the crystallinity and concentration of the A-site cations,resulting in the stable mixed halide perovskite Cs Pb Cl_1.2Br_1.8,which provides a reference for the application of mixed halide perovskites in optoelectronic devices.