Research On Compensation Mechanism Of Ion Deficiency And Optical & Electrical Properties Under The Lattice Control Of Perovskite Material

As a new type of photoelectric material,halide perovskite has attracted wide attention.However,due to its ion migration characteristics,irreversible ionization will occur,resulting in the appearance of ion deficiency and a large number of ion defects in the material,which is the main reason for the lattice dissociation and the reduction of luminescence properties of perovskite.The undercoordinated metallization of Pb²⁺can also lead to lattice dissociation,which is harmful to human body and natural environment.Therefore,it is particularly important to study how to make up for the ion vacancy and avoid the metallization of Pb²⁺.In this paper,the 113 type halide perovskite material CsPbX₃（X=Br,I）is studies as research object firstly.By clarifying the influence of ion defects on the lattice,the lattice is regulated by doping ions to achieve the effect of ion deficiency compensation and ion migration inhibition.At the same time,the lead-free double perovskite Cs₂Na Bi Cl₆was selected as the research object,and the corresponding doping strategy was carried out to reduce the ion defects.According to its characteristics,it was applied in the field of lithium battery.The main research contents are as follows:（1）The effects of ion deficiencies on the lattice structure and optical properties of CsPbBr₃perovskite quantum dots were studied.CsPbBr₃quantum dots with Cs⁺ion vacancies were synthesized by cationic thermal implantation in Br rich reaction environment,and CsPbBr₃quantum dots with Br^-ion vacancies were synthesized by anionic thermal implantation in Br^-poor reaction environment.The ion vacancies of both of them led to the distortion of local lattice,resulting in the metallization of incomplete coordination of Pb²⁺and the reduction of fluorescence lifetime,Among them,the proportion of composite defect-assisted lifetime increases.（2）The effect of Rb⁺substitution on the lattice structure and optical properties of CsPbBr₃perovskite quantum dots was studied.With the increase of Rb⁺concentration,Cs⁺sites are occupied continuously,which changes the charge environment in the lattice structure and makes the Pb-Br-Pb bond angle smaller,and the[Pb Br₆]^4-octahedron is twisted,and the compressed conduction band structure of CsPbBr₃leads to the increase of band gap.Therefore,the position of emission peak and the edge of absorption band are blue shifted with the increase of Rb⁺concentration.In addition,a small amount of Rb⁺ions doping can reduce the vacancy of monovalent cations,improve the fluorescence lifetime and luminescence efficiency of CsPbBr₃,and improve the stability of the structure.However,a large amount of Rb⁺ions doping can produce a large number of vacancy,which promotes the lattice dissociation.（3）The passivation effect of LiBr as a double defect passivator in CsPbX₃（X=Br,I）structure was studied.The introduction of LiBr can not only provide Br^-to fill the halogen vacancy,but also introduce Li⁺into the lattice gap,which can stabilize the halogen and inhibit the halogen migration through the traction force on the surrounding halogen to avoid the occurrence of uncoordinated Pb²⁺,and free electrons can also be provided to passivate the intrinsic hot electron defects,which eventually increases the fluorescence lifetime of CsPbBr₃,and decreases the proportion of defect recombination lifetime.In addition,the existing position of Li⁺and its influence on the lattice structure are also clarified,and the related passivation mechanism is proposed,which lays a foundation for the subsequent study of Li⁺intercalation and de intercalation in perovskite lattice.（4）Based on the action mechanism of Li⁺for halide perovskite,a high concentration of Li⁺doping in 2116 type lead free double perovskite Cs₂Na Bi Cl₆was achieved by grinding method.In addition,when it is used as anode material of lithium battery,the first charge discharge specific capacity of 775m A h g^-1can be achieved,and after 25 cycles,the cycle specific capacity can still be maintained at 300m A h g^-1,and the coulomb efficiency is close to 100%,which lays the foundation for the application of double perovskite materials in lithium battery electrode materials and expands the application field of perovskite materials.