Study On The Stability And Optical Properties Of Inorganic Halide Perovskite Nanocrystals

Recently,as a kind of superior semiconductor photoelectric materials,perovskite quantum dots have drawn more and more attention.Among which,inorganic halide perovskite quantum dots(IHPQDs)arouse the research trend because of their excellent optical properties,such as tunable emission wavelength,high color purity,wide color gamut,high defect tolerance and high photoluminescence quantum yield et.al,which help them become a kind of promising materials in the application of many optoelectronic devices.However,due to the nature of their ionic crystals and the appearance of surface defects easily in IHPQDs,the stability of IHPQDs is unsatisfied which may even limit their applications.Therefore,how to improve their stability while improving their optical properties is an urgent problem to be solved as soon as possible at present.In this thesis,we use surface modification and inorganic coating to modify the surfaces of IHPQDs,and successfully synthesized a series of different kinds of CsPbX₃ nanocrystals.These CsPbX₃nanocrystals not only exhibit excellent optical properties,but also show good stability,and the white light-emitting devices(WLED)prepared by these could emit high quality white light.The main contents of this paper are as follows:Firstly,we designed a kind of novel bromide quaternary ammonium ligand,and successfully prepared CsPbBr₃ QDs with the help of room-temperature supersaturated recrystallization.These CsPbBr₃ QDs are cubic phase,with full width at half maxima(FWHM)of only 17 nm and photoluminescence quantum yield(PLQY)of 95%.Moreover,we have also successfully fabricated white light-emitting diodes(WLED)by combining these QDs with traditional cadmium selenide QDs.The color coordinate of the WLED is(0.29,0.31),which is close to the color coordinate of the standard WLED(0.33,0.33),and the color gamut of this WLED covers 130%of the color gamut of the National Television Standards Committee(NTSC).Secondly,we learned about how thiol groups affect CsPbI₃ QDs through surface modification,and we synthesized treated CsPbI₃ QDs with high quality and stability after adding octadecanethiol(ODT)to CsPbI₃ QDs synthesized via hot injection method.Compared to the untreated samples,PLQYs of treated CsPbI₃ QDs almost doubled,besides,the stability of treated samples in atmosphere and the ultraviolet light resistance of them were improved greatly.We also proved that ODT could passivate the surface of CsPbI₃ QDs better than traditional ligands through the experimental results and First Principle Calculation results based on the density functional theory.Thirdly,we put different PbX₂ salts and CsX salts on Anodic Aluminum Oxide(AAO)templates,and successfully fabricated CsPbBr₃ nanorods coated in AAO templates(CsPbBr₃@AAO)via high temperature sintering method.CsPbBr₃@AAO not only exhibit50.76%PLQY,but also show outstanding stability in every kind of extreme environments due to the protection of stable and dense AAO.As a result,the photoluminescent intensity of CsPbBr₃@AAO could maintain 95%of the initial state even after soaked in water for 48hours.The outstanding stability and good optical properties of CsPbBr₃@AAO make it possess a great prospect in the application of optoelectronic devices.