Study On Photophysical Properties And Stability Of Lead-based Halide Perovskite Quantum Dots

Lead-based halide perovskite quantum dots(CsPbX3 PQDs,X=I,Br,Cl)have attracted much attention due to their excellent optical properties,such as high photoluminescence quantum yield(PL QY),narrow full width at half maxima(FWHM),and tunable wavelength.Despite the merits of CsPbX3 PQDs,the inherent instability and poor reliability of CsPbX3 PQDs seriously impede practical applications,which bring a great challenge to commercialization.At present,the synthesis strategies of CsPbX3 PQDs are mainly hot injection method and supersaturated recrystallization method,but they all have corresponding problems.For example,the hot-injection method often needs inert gas protection to complete the whole reaction process and reaction temperature is relatively high.Supersaturated recrystallization to prepare the high iodide-substituted Cs Pb Br3-x Ix PQDs still faces great challenge because of their poor stability in air.Although applying surface coatings to PQDs or embedding them in organic/inorganic materials can improve instability,organic matrix has poor heat resistance,and the thick shell layer of inorganic materials will affect the optical properties of PQDs.Therefore,it is necessary to solve the instability of CsPbX3 PQDs.In order to overcome these problems,this article has adjusted and optimized the CsPbX3 PQDs preparation process and stability strategy.The specific work is as follows:(1)We developed a simple and low-cost strategy for preparing highly luminescent and air-stable all inorganic PQDs by directly heating perovskite precursors in octane in air.The emission wavelength of PQDs can be tunable from ultraviolet(UV)to infrared region by simply controlling their halide composition and size.Moreover,PQDs in octane can exist more than half a year in air and the film of PQDs also shows good thermal stability and air stability,especially high iodide-substituted Cs Pb Br3-x Ix PQDs.The PQDs can be easily blended with PDMS and used as color conversion layer on the blue LEDs chip for high quality white LEDs.The optimized devices have a luminous efficacy of 40.3 lm W^-1 at a current density of 15 m A with coordinate value of(0.32,0.33)and bright pure white light.Our work opens a window for the potential applications of this highly luminescent material in the fields of multicolor LEDs,backlight displays and other related optoelectronic devices.(2)Highly-luminescence and ultra-stable phosphor were obtained by loading PQDs onto the surface of amino modified hexagonal boron-nitride(h-BN)white graphene(PQDs-BNWG),this structural design can effectively suppress the attenuation of photoluminescence(PL)intensity and enhance thermal stability,thereby realizing the high stability and brightness white LEDs.The synthesis process is simple and can be finished in a few minutes to ensure scalable production.Compared with bare PQDs,it can maintain excellent optical properties.The high PL QY and thermal stability mainly stem from the isolation effect that separates PQDs from each other on the surface of BNWG and their superior high transparency as well as thermal conductivity.In addition,multi-color inks are produced by dispersing PQDs-BNWG nanocomposites in PDMS to form a multicolor painting demonstrating high PL QY and wide color gamut.