Temperature-dependent energy transfer dynamics in InP/MnxZn­1-xS core/shell quantum dots

Abstract

Manganese-doped quantum dots have been explored for a variety of applications, including as display phosphors, light absorbers for photocatalysis and photovoltaics, and in quantum information technologies. The majority of work on Mn-doped quantum dots employs either heavy metal-containing hosts (Cd or Pb) or UV-absorbing hosts (ZnS or ZnSe). Manganese doping in the heavy metal free, visible-light-absorbing, InP quantum dot material is relatively underexplored. In particular, only a handful of studies probe the excited state dynamics in these materials. To build a deeper picture of the photophysics in these materials, the current work employs InP/Mn_xZn_1-xS core/shell quantum dots with varying Mn concentrations. Temperature-dependent and time-resolved photoluminescence spectroscopy is used to explore the forward and reverse energy transfer between the InP excitonic state and the excited Mn state. We find that the InP to Mn energy transfer rate constant is proportional to Mn concentration. Furthermore, we show that an equilibrium exists between these two states that can be well understood with Boltzmann statistics and allows for thermally-activated delayed photoluminescence from the InP exciton (∼4 ms).