Mengling Xia

Surface Passivation of CdSe Quantum Dots in All Inorganic Amorphous Solid by Forming Cd 1−x Zn x Se Shell

CdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd1−xZnxSe shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/Cd1−xZnxSe core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials.

Influence of Pr3+ doping on the microstructure of ZnO quantum dots

Pr3+ doped ZnO quantum dots (QDs) were successfully synthesized by sol-gel process. X-ray diffraction (XRD) and X-ray Phtoelectron spectroscopy (XPS) were used to analyze the microstructure variation of ZnO QDs and the chemical environment of Pr3+ with increasing Pr3+ doping concentrations. Most of Pr3+ ions distribute on the surface of ZnO QDs while a few of them penetrate into the ZnO lattice to substitute Zn2+ which causes the lattice distortion and the change of the crystal size. With increasing concentration of Pr3+ ions, the crystal size of ZnO QDs firstly increases and then decreases meanwhile the amorphization gradually increases. New Pr-O-Zn bonds formed after Pr3+ doping and Pr3+ ions have at least two chemical bonding environments: one is Pr-O-Zn bond and the other is Pr-O bond surrounded by oxygen vacancies.

Optical properties and charge carrier dynamics of CdTe quantum dots in silicate glasses

CdTe quantum dots (QDs) in silicate glasses were fabricated through conventional melt-quenching and heat-treatment; steady-state and transient optical properties of CdTe QDs were investigated. CdTe QDs with diameters of 2.3–5.9 nm with photoluminescence in the range of 553–768 nm were precipitated in the glasses. Time-resolved photoluminescence and transient absorption analysis showed that photoluminescence of CdTe QDs was composed of intrinsic emission and defect emission. Oxidation of Te2− and formation of Te2 during thermal treatment led to the unpassivated Cd2+ on the surface of CdTe QDs and formation of shallow trapping states. The photo-generated electrons were trapped by the shallow surface states of CdTe QDs within 0.4±0.03 ps, and Auger recombination processes occurred within a timescale of 3.2±0.35 ps. Both intrinsic emission and defect emission with effective lifetimes of several nanoseconds and dozens of nanoseconds were observed.