Construction Of Multiscale Microstructures And Luminescence Tuning Of Doped Quantum Dots

Doped semiconductor quantum dots(QDs)have demonstrated attractive applications in recent years since they simultaneously contain the intrinsic optical properties of the QD materials and the luminescence properties of the doped activators.In this dissertation,transition metal ions doped Ⅱ-Ⅳ QDs and all inorganic CsPbX3 perovskite quantum dots are selected as research objects.The main research results in this paper are as follows:(1)The optimized ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multi-shell QDs have been prepared,and their luminescence properties depending on the ratios of the starting materials and the injection temperature of extra sulfur source were discussed.As a controlled synthesis comparison,the optimum core/shell structures and key synthesis parameters have been determined,and the quantum yield of the as-obtained ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multi-shell white light emitting QDs without defect emission was determined to be 38%.(2)We prepared the colloidal CdS/ZnS/ZnS:Mn2+/ZnS core/multi-shell QDs which show blue and orange emission simultaneously.Their emission intensity ratios are dependent on the power-density of a single-wavelength excitation source.Finally,we used the color-tunable colloidal core/multi-shell QDs for anti-counterfeiting applications.(3)We used a novel strategy for the synthesis of Cs(PbxMn1-x)(ClyBr1-y)3 QDs via a post-synthetic cation-anion cosubstitution exchange reaction to tailor their optical properties in a wide range.Colloidal CsPbBr3 and CsPb1-xMnxCl3 QDs are firstly prepared,respectively,and then mixed each other in hexane solution.Pb2+and Br-ions in CsPbBr3 QDs are simultaneously exchanged for Mn2+ and Cl-ion in CsPb1-xMnxCl3 QDs,resulting in homogeneous Cs(PbxMn1-x)(ClyBr1-y)3.(4)Benefiting from the differentiation of the cation/anion exchange rate,we demonstrate that ZnBr2 and preformed CsPb1-xCl3:xMn QDs can be used to obtain high Br content Cs(Pb1-x-zZnz)(ClyBr1-y)3:xMn2+ perovskite QDs with strong Mn2+emission,and Mn2+ substitution ratio can reach about 22%.The Mn2+ emission intensity could be further varied by controlling the replacement of Mn2+ by Zn2+with prolonged ion exchange reaction time.White light emission of the doped perovskite QDs could be realized via this cation/anion synergistic exchange strategy.(5)When CsPbX3 QDs was treated by ZnX2,the halogen ions in ZnX2 will fill the surface defects of CsPbX3 QDs.When CsPbX3 QDs was treated with water,the ions on the surface of the QDs will dissolved into water and made the inner layer become a new surface layer,which could also eliminated the surface defects.The elimination of surface defects significantly enhanced the stability and luminescence properties of CsPbX3 QDs.