Study On White LED Based On All-inorganic Perovskite Quantum Dots And Composite Materials

All-inorganic perovskite CsPbX₃?X=Cl,Br,I and Cl/Br and Br/I mixed halide systems?QDs have attracted considerable attention owning to their excellent luminescence properties,such as high photoluminescence?PL?quantum yield?QY?,the emission could be tuned over the entire visible spectral,and have been widely studied and recognized as promising materials for optoelectronic devices,especially in white LEDs.Despite their potential,they have some inherent disadvantages,such as degradation under operating conditions driven by humidity,light and temperature,as well as low stability and limited processability,hindering their commercial application.To this end,this paper proposes to combine quantum dots with different compounds or polymers to improve quantum dot stability.The structure,morphology,optical properties and optoelectronic properties of quantum dot solutions and composites will be analyzed through a series of modern analytical testing systems.The specific research contents are as follows:1.Preparation and properties of CsPbX₃ quantum dots and CsPbX₃/ITO composite structures.The all-inorganic perovskite quantum dots which are adjustable in the visible light range are obtained by a thermal injection method and an anion exchange method.Since anion exchange reaction is highly prone to occur between quantum dots,in this paper we chosen ITO?indium tin oxide?as a barrier layer to prevent anion exchange reaction between different perovskite QDs.we present a sandwich WLEDs layer structure of ITO film+three blue-,yellow-and/or red-emitting perovskite QDs phosphors+UV-emitting chip,through changing the layer ratio among blue-,yellow-and/or red-emitting QDs/ITO films on UV-emitting chip,we realize the tunable WLEDs from cool light to warm light successfully.2.Preparation of CsPbX₃ quantum dot and PDMS composite structure and study on its luminescent properties of flexible white LED.The prepared quantum dots are dispersed in polydimethylsiloxane?PDMS?to obtain a CsPbX₃/PDMS flexible film composite,which effectively improves the stability of the perovskite quantum dots.It is explained the mechanism that quantum dots are stable in PDMS by transient spectroscopy.In addition,the tunable white LED is composed of a prepared blue CsPbCl_1.58Br_1.42/PDMS film and a orange CsPbI_1.65Br_1.35/PDMS film combined with a UV chip.The corresponding white LED CCT from 5901 K to 3194 K indicates a tunable WLED from cold light to warm light,which clearly indicates that the material is expected to be used in flexible lighting devices.3.Preparation and luminescent properties of CsPbBr₃ quantum dots and different crystalline TiO₂ composite structures.The composite structure of CsPbBr₃ quantum dots and different crystalline TiO₂ films was subjected to UV absorption,fluorescence spectroscopy,XRD and fluorescence lifetime test at room temperature to investigate the effect of different crystal structure of titanium dioxide on the optical properties of CsPbBr₃ quantum dots.