Functionalized Porphyrin Surface-Modulated Synthesis Of Stable Perovskite Nanocrystals And Their Properties Study

Lead halide perovskites materials have gained wide attention for their excellent optoelectronic properties such as tunable band gap,high optical absorption coefficient,good carrier transport capability,and high defect tolerance.Compared with bulk perovskites materials,perovskites nanocrystals have more outstanding physicochemical properties,not only possessing excellent solution handling characteristics of colloids,but also having extremely high luminescence quantum yields,tunable luminescence wavelengths in the entire visible spectrum,and responsiveness to external stimuli.However,due to their inherent ionic nature,the oleic acid（OA）and oleylamine（OAm）ligands on the surface of perovskites nanocrystals are in a highly dynamic binding state and are highly susceptible to detachment during preparation and preservation,resulting in the formation of a large number of defects on the surface.Therefore,perovskites nanocrystals are very sensitive to environmental factors such as humidity,temperature and light,and are susceptible to environmental factors,which can lead to phase change or even decomposition when stored for a long time,thus limiting his further applications.Therefore,how to improve the stability of perovskites nanocrystals is an important challenge in the field of perovskites nanomaterials research.In this thesis,introduced functional molecules with high coordination ability groups through molecular design to improve the stability of perovskites nanocrystals while giving them certain properties.The specific research for this thesis work is as follows:To improve the stability of the organic-inorganic hybrid perovskite nanocrystals,introduced 4,4’,4",4"-（porphyrin-5,10,15,20-tetrayl）tetrakis（benzene-sulfonic acid）（TPPS）to passivate CH₃NH₃Pb Br₃ perovskite nanocrystals instead of oleic acid（OA）ligands.Various concentrations of TPPS solution ware added into the precursor solution to passivate surface defects.The experimental results show that the optimal doping amount for TPPS is 80μL(0.04 mmol L^-1).And the fluorescence quantum yield of TPPS passivated MAPb Br₃ was 65%,which is two times higher than that the unpassivated material.In addition,the introduction of TPPS ligands can not only effectively eliminate lead vacancies,but also enhance the water,UV light,and thermal stability of the material.Due to the excellent optical performance and enhanced stability of TPPS-MAPb Br₃,it can be prepared into efficient anti-counterfeiting labels.This type of encryption method not only greatly improves the security of data,but also provides another method for data storage and information encryption.In order to further improve the stability of all inorganic perovskite nanocrystals.We designed and synthesized a red luminescent thiol porphyrin（Por-SH）as a ligand to modify the surface of Cs Pb Br₃ perovskite nanocrystals.In conclusion,a red fluorescence Por-SH is applied to regulate the surface of Cs Pb Br₃ QDs,which can not only maintain the original Cs Pb Br₃ structure but also enhance the environmental stability.This leads to a hydrophobic layer because of the tertiary butyl group of Por-SH,thus preventing the adsorption of water by the Por-SH-QDs.Por-SH can tightly adhere to the surface of quantum dots,enhancing their UV stability,and also endowing them with responsiveness to stimuli.By taking advantage of the enhanced stability and dualresponsive PL emission of Por-SH-QDs,inspire us to design of complex high-level optical anti-counterfeiting patterns appropriate for different purposes.According to various fluorescence emissions of Por-SH-QDs and QDs under dual stimulation,one-time or reversible optical encoded tags can be obtained.This work provides a feasible solution for improving the stability of perovskite through the rational design of surface ligands,enriches the stimulus response of quantum dots,and can expand their application range in various optical anti-counterfeiting materials.