Micro-nano Structure Control And Light Absorbance Study On CH₃NH₃PbX₃?X=I,Br? Mixed Halide Perovskite

CH₃NH₃PbX₃?X=I,Br?mixed halide perovskite has attracted great attention due to its outstanding optoelectronic properties and a wide variety of applications.Understanding the growth of mixed halide perovskite crystal would benefit the fundamental studies of materials and further improve their applications.However,the influence of the halogen element content in the reaction precursor and reaction parameters on the crystal composition and band gap of the mixed halide perovskite has been a controversial issue,and research on its formation mechanism has rarely been reported.In this paper,firstly,the lead halide nanowires with different bromine content were prepared by reprecipitation,and then they were used as the reaction precursors.R1,R2,R3 and R4 series experiments were carried out using common solution processing methods,and a series of characterizations were carried out to systematically study the formation mechanism of mixed halide perovskite.The main research is as follows:?1?We have obtained four series of mixed halide perovskite of R1-1,R1-2,R1-3 and R1-4 by reacting different composition of lead halide nanowires and different concentrations of MAX?X=I,Br?/IPA solution.It is found that the halogen element composition of the mixed halide perovskite is linearly dependent on the halogen element composition of the lead halide nanowire.And by controlling the composition of the reaction precursor,coarse tuning of the composition and band gap of the mixed halide perovskite can be achieved in a low concentration of MAX?X=I,Br?/IPA solution,while fine tuning can be achieved in a high concentration of MAX?X=I,Br?/IPA solution.?2?The reaction of lead iodide?or lead bromide?with different concentrations of MAI/IPA?or MABr/IPA?was studied in time-dependent studies.The results show that the growth of perovskite crystals goes through two stages.The first stage is the dissolution of the reaction precursor and the formation of Pb[Br₃I]^2-ion.The second stage is the growth of mixed-halide perovskite crystals,and the concentration of MAX/IPA solution has an important effect on it.Crystal growth follows the Oswald ripening mechanism in low concentration MAX/IPA solution,and the crystals were grown in a high concentration MAX/IPA solution by a dissolution-recrystallization mechanism.?3?Two series of mixed halide perovskite of R4-1 and R4-2 were obtained by reacting lead iodide?or lead bromide?and MAX?X=I,Br?/IPA solution with different molar fractions of MABr.The results show that lead halide composition and MAX?X=I,Br?/IPA solution composition will affect the micro-nano structure of the mixed halide perovskite.The micro-nano structure of the perovskite crystal can be controlled by controlling the composition of the reaction precursor and the composition of the MAX?X=I,Br?/IPA solution.