Preparation,Modification,and Application Of Perovskite Based On Cesium Lead Halide

CsPbX₃（X=Cl,Br,I）nanocrystals are a new type of light trapping and luminescent material compared to conventional semiconductor materials.They have an excellent performance in strong light absorption,solution processability,morphology adjustability,and accurate band gap tunability across the entire visible spectrum range.Moreover,it can be widely used in the fields of semiconductor devices and integrated optoelectronics.However,the luminescent performance and stability of Cs Pb X₃（X=Cl,Br,I）nanocrystals still need improvements.In addition,there is a need to expand its application areas further.Therefore,improving the luminescent performance and stability of Cs Pb X₃（X=Cl,Br,I）nanocrystals and expanding their applications is of great importance for in-depth research in the field of perovskite.Element ion doping can be used as an effective method to adjust the basic properties of Cs Pb X₃（X=Cl,Br,I）perovskite nanocrystals.Its advantage is that the original crystal structure of the material remains unchanged,and the size,shape,and composition of the initial（parent）perovskite nanocrystals can be adjusted by using different ion sources as templates.Element ion doping is a flexible and efficient method.Therefore,elemental doping of Cs Pb X₃（X=Cl,Br,I）nanocrystals could improve the luminescence performance and stability.Based on the above background,Cs Pb I₃ perovskite nanocrystals were prepared in this dissertation.Subsequently,the luminescent properties of Cs Pb I₃ nanocrystals were improved through halogen ion doping.Additionally,the dissertation investigates the application of perovskite nanocrystals in fluorescent anti-counterfeiting,LED lighting,and fiber fields.Furthermore,based on the research of Cs Pb X₃ nanocrystals,the dissertation further investigates lead-free double perovskite Cs₂Na Bi X₆（X=Cl,I）nanocrystals with three-dimensional（3D）structure and outstanding physical and photoelectronic properties.This dissertation investigates their preparation methods,properties,and applications.The specific research contents are as follows:（1）A novel and convenient synthesis strategy was adopted in this dissertation to prepare Cs Pb I₃ perovskite nanocrystals,and the preparation process and properties of Cs Pb I₃ perovskite nanocrystals were specifically studied.These Cs Pb I₃ nanocrystals were synthesized at a low reaction temperature,without the involvement of certain gases,under normal pressure.We investigated the reaction kinetics of Cs Pb I₃nanocrystals by exploring experimental parameters and adjusting reaction time and temperature.The dissertation focuses on Cs Pb I₃ nanowires,which are arranged in an orthogonal pattern.The synthesis method was simple,safe,and low-cost.Moreover,the synthesized nanowires were prepared at low temperatures and performed well.This preparation method has laid the foundation for subsequent performance improvement and application research of perovskite.（2）In this dissertation,a halogen ion post treatment modification strategy was introduced to improve the performance of Cs Pb I₃ perovskite nanocrystals and achieve application.Moreover,the zinc bromide（Zn Br₂）/hexane solution was used as a post treatment solution in Cs Pb I₃ perovskite nanocrystals to improve the perovskite system.Experiments were carried out to post-treat Cs Pb I₃ nanowires and Cs Pb I₃ nanorods,respectively.Both post-treated nanocrystals showed improved properties and maintained good regular morphology,and the post-treated nanorods exhibited good luminescence properties and high photoluminescence quantum yields（PLQY=89%）.We prepared fluorescent anti-counterfeiting paper by combining the modified nanorod solution with aramid/polyphenylene sulfide composite paper（characteristic of our research group）.The fluorescent anti-counterfeiting papers can achieve multi-field applications of perovskite nanocrystals,and this study has laid a solid foundation for their applications in the perovskite and fiber fields.（3）Nanocrystals of double perovskite Cs₂Na Bi X₆（X=I,Cl）were investigated in the dissertation.Nanocrystals of double perovskite Cs₂Na Bi I₆ were synthesized using a simple and effective method in the dissertation,and their morphology and crystal structure were characterized.Then,lead-free double perovskite Cs₂Na Bi Cl₆nanocrystals were synthesized by hydrothermal and thermal injection methods,respectively.The morphology,structure,and properties of the Cs₂Na Bi Cl₆ nanocrystals synthesized by the two methods were then compared.Furthermore,the performance of Cs₂Na Bi Cl₆ nanocrystals synthesized by the hydrothermal method was enhanced by doping with the rare earth element Eu³⁺,and their applications were explored.