Synthesis Of All Inorganic Perovskite Nanocrystals For LED Application

Lead-halide perovskite nanocrystals have attracted widespread attention as an emerging photoelectric material,especially all inorganic perovskite nanocrystals,due to their excellent optical properties,such as high photoluminescence quantum yield,narrow full-width at half maximum,easy to adjust the emission wavelength by composition and size,the synthesis method is simple and easy,and the cost is low.It has broad application prospects in solar cells,light-emitting diodes,photodetectors and other fields.The currently reported synthetic methods mainly include high temperature hot injection and room temperature supersaturation recrystallization.Since all inorganic perovskite nanocrystals are very sensitive to polar solvents and surfactants,so improving its stability has been the focus of research in recent years.In order to improve the stability of all inorganic perovskite nanocrystals,nano-scaled encapsulation by in-situ capping Si O₂ and embedding into PMMA matrix composites,to achieve a stable perovskite light converting composite sheet for LED remote-type encapsulation.In addition,since the all inorganic perovskite nanocrystals synthesized at room temperature are unstable,the all inorganic perovskite nanocrystals synthesized at room temperature have lower stability than the all inorganic perovskite nanocrystals synthesized at high temperature,therefore,we try to improve the stability of all inorganic perovskite nanocrystals in halide-rich circumstance,and the corresponding LED devices are prepared.The specific work is as follows:(1)A new hierarchy encapsulation method is proposed,integrated with surface modification by halide ions protection,nano-scaled encapsulation by in-situ capping Si O₂ and embedding into PMMA matrix composites,to achieve a stable perovskite light converting composite sheet for LED remote-type encapsulation,ie Pe NCs/Si O₂/PMMA,which was compared stability with Pe NCs/PMMA,Pe NCs/PMMA was prepared from all-inorganic Cs Pb Br₃ perovskite nanocrystals without silica coating.The 2D maps of spectra and aging measurement indicate that the silica encapsulation can well protect the Pe NCs in PMMA matrix from the ambient circumstance during a long-term storage process.Additionally,the hierarchic encapsulation for Pe NCs/Si O₂/PMMA showed the better operational stability than the direct encapsulation of Pe NCs/PMMA,and the correspondent Commission Internationale de L'Eclairage(CIE)color coordinates tracking also indicated more stable color properties(2)It was found through experiments that the Cs Pb Br₃ perovskite nanocrystals synthesized at room temperature are not as stable as the Cs Pb Br₃ perovskite nanocrystals synthesized at high temperature,so we proposed to improve the stability of Cs Pb Br₃perovskite nanocrystals synthesized at room temperature in halide-rich circumstance,the corresponding LED device was fabricated.The current efficiency of the LED device prepared by the Cs Pb Br₃ perovskite nanocrystal synthesized in halide-rich circumstance reached 10.06cd/A,and the external quantum efficiency was up to 3.88%.While the LED device prepared by the Cs Pb Br₃ perovskite nanocrystals synthesized in conventional methods has a current efficiency of 7.43 cd/A and an external quantum efficiency of up to 2.53%.