Post-Passivation Treatment Of CsPbX₃ Perovskite Quantum Dots Based On Double Ion Synergistic Effect And Their Optical Properties

In recent years,all-inorganic CsPbX₃（X=Cl,Br,I）perovskite quantum dots have become a kind of promising and emerging semiconductor nanomaterial due to their excellent optoelectronic properties,which is expected to be applied in new-generation optoelectronic applications such as light-emitting diodes（LEDs）,solar cells,lasers,photodetectors and thin-film transistors.However,owing to its inherent ionic properties,low formation energy,highly dynamic surface ligands and massive surface defects,CsPbX₃ quantum dots are easily affected by the external environment.Under the induction of light,heat,water,oxygen,polar solvents and other factors,CsPbX₃quantum dots are prone to hydrolysis,decomposition,oxidation and phase transition,which will destroy their crystal structure and deteriorate their optical properties.Therefore,the poor environmental stability of CsPbX₃ quantum dots has seriously hindered its industrialization process.Based on this,in this paper,post-passivation treatments using the guanidine hexafluorophosphate（Gua PF₆）solid powder and nickel tetrafluoroborate（Ni（BF₄）₂）solution are used to prepare CsPbX₃ quantum dots,which can effectively improve their optical properties and environmental stability.Additionally,the post-passivation-treated CsPbX₃ quantum dots are successfully applied to white light-emitting diodes（WLED）.The main research contents are as follows:Firstly,an appropriate amount of Gua PF₆ solid powder is added to the fresh CsPbX₃（X=Cl,Br,I）quantum dot colloidal solution for post-passivation treatment.The results show that Gua PF₆ can effectively passivate the surface defects of CsPbX₃quantum dots through the synergistic effect of Gua⁺and PF₆^–without changing the crystal structure of quantum dots,thus significantly improving the photoluminescence quantum yield（PLQY）and environmental stability of CsPbX₃ quantum dots.In addition,the Gua PF₆-post-passivation-treated Cs Pb Br₃ quantum dots are successfully applied to the device for obtaining WLED with bright white light and good stability.Secondly,post-passivation treatment of Ni（BF₄）₂ solution for Cs Pb Br₃ quantum dots are conduced,which can significantly boost their optical properties and environmental stability.The results show that the PLQY of Cs Pb Br₃ quantum dots is most ignificantly increased when the concentration of Ni（BF₄）₂ solution is 20 mmol L^-1.Benefiting from the synergistic effect of Ni²⁺doping into the quantum dot lattice for stabilizing the perovskite lattice,as well as BF₄^–passivating the surface Br vacancies,the PLQY and stability of Cs Pb Br₃ quantum dots are significantly improved.In addition,the post-passivation-treated Cs Pb Br₃ quantum dots using the Ni（BF₄）₂solution are successfully applied to WLED with bright warm white light and good stability.In this paper,the dual-ion synergistic post-passivation treatment strategy is applied to prepare CsPbX₃ perovskite quantum dots exhibiting robust photoluminescence and environmental stability,and such CsPbX₃ perovskite quantum dots are successfully applied to WLED devices.Our work provides a new route and approach for improving the photoluminescence properties and stability of CsPbX₃perovskite quantum dots.