Zhicheng Su

A set of manganese ion activated fluoride phosphors (A2BF6:Mn4+, A = K, Na, B = Si, Ge, Ti): synthesis below 0 °C and efficient room-temperature photoluminescence

Transition-metal ion activated solid-state phosphors are of particular interest for the development of LED-based white light sources. In addition to their relatively low cost, these luminescent materials show exceptionally high luminescence efficiency, especially at room temperature and above, due to the involvement and promotion of thermal phonons. In this article, we present a comprehensive investigation into a set of manganese ion doped fluoride phosphors (A2BF6:Mn4+, A = K, Na, B = Si, Ge, Ti), including the synthesis procedures and various characterization, with the emphasis on optical spectroscopic characterization. All of the phosphors synthesized at a temperature of −16 °C using a chemical co-precipitation method exhibit intense red color emission at room temperature under the excitation of light, with a wide range of wavelengths from 450 nm to 325 nm. In most of the phosphors, phonon-assisted luminescence dominates the spectra, which is evidenced using Raman scattering measurements. X-ray diffraction data from the samples reveal that K2SiF6:Mn4+ crystallizes in a cubic phase, while the remaining crystals have hexagonal structures, but with different symmetries for K2TiF6:Mn4+ and Na2SiF6:Mn4+. More interestingly, well-resolved spectral splitting was observed in the major phonon-assisted luminescence signatures of both the K2SiF6:Mn4+ and K2TiF6:Mn4+ samples, indicating the occurrence of complicated but fascinating phonon-assisted transition processes in the phosphors.

A generalized model for time-resolved luminescence of localized carriers and applications: Dispersive thermodynamics of localized carriers

AbstractFor excited carriers or electron-hole coupling pairs (excitons) in disordered crystals, they may localize and broadly distribute within energy space first, and then experience radiative recombination and thermal transfer (i.e., non-radiative recombination via multi-phonon process) processes till they eventually return to their ground states. It has been known for a very long time that the time dynamics of these elementary excitations is energy dependent or dispersive. However, theoretical treatments to the problem are notoriously difficult. Here, we develop an analytical generalized model for temperature dependent time-resolved luminescence, which is capable of giving a quantitative description of dispersive carrier dynamics in a wide temperature range. The two effective luminescence and nonradiative recombination lifetimes of localized elementary excitations were mathematically derived as

Excitation Dependent Phosphorous Property and New Model of the Structured Green Luminescence in ZnO

{{\boldsymbol{\tau }}}_{{\boldsymbol{L}}}{\boldsymbol{=}}\frac{{{\boldsymbol{\tau }}}_{{\boldsymbol{r}}}}{{\bf{1}}{\boldsymbol{+}}\tfrac{{{\boldsymbol{\tau }}}_{{\boldsymbol{r}}}}{{{\boldsymbol{\tau }}}_{{\boldsymbol{t}}{\boldsymbol{r}}}}({\bf{1}}{\boldsymbol{-}}{{\boldsymbol{\gamma }}}_{{\boldsymbol{c}}}){{\boldsymbol{e}}}^{({\boldsymbol{E}}{\boldsymbol{-}}{{\boldsymbol{E}}}_{{\boldsymbol{a}}}){\boldsymbol{/}}{{\boldsymbol{k}}}_{{\boldsymbol{B}}}{\boldsymbol{T}}}}

Structural Dependences of Localization and Recombination of Photogenerated Carriers in the top GaInP Subcells of GaInP/GaAs Double-Junction Tandem Solar Cells

τL=τr1+τrτtr(1−γc)e(E−Ea)/kBT and

Large Negative-Thermal-Quenching Effect in Phonon-Induced Light Emissions in Mn4+-Activated Fluoride Phosphor for Warm-White Light-Emitting Diodes

{{\boldsymbol{\tau }}}_{{\boldsymbol{n}}{\boldsymbol{r}}}{\boldsymbol{=}}\frac{{{\boldsymbol{\tau }}}_{{\boldsymbol{t}}{\boldsymbol{r}}}}{({\bf{1}}{\boldsymbol{-}}{{\boldsymbol{\gamma }}}_{{\boldsymbol{c}}})}{{\boldsymbol{e}}}^{{\boldsymbol{-}}({\boldsymbol{E}}{\boldsymbol{-}}{{\boldsymbol{E}}}_{{\boldsymbol{a}}}){\boldsymbol{/}}{{\boldsymbol{k}}}_{{\boldsymbol{B}}}{\boldsymbol{T}}}

Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

τnr=τtr(1−γc)e−(E−Ea)/kBT, respectively. The model is successfully applied to quantitatively interpret the time-resolved luminescence data of several material systems, showing its universality and accuracy.