Time-Resolved Photoluminescence Study of MnS/ZnS Core/Shell Quantum Dots at High Pressure and Low Temperature

Time-resolved photoluminescence experiments of MnS/ZnS core/shell QDs were performed at high pressure up to 11.7 GPa and low temperature down to 80 K. Four main emission components are observed and discussed: (1) an ultrafast broad blue-green peak attributed to ultrafast defects emission, (2) an ultrafast ultraviolet peak at about 390 nm attributed to exciton emission, (3) a fast blue peak attributed to fast defects emission, and (4) the slow (MnT1)-T-4((4)G) orange emission. With increasing pressure, the exciton emission shows blue shift as the band gap increases. TheMn(4)T(1)((4)G) emission has different pressure shift rates at different time delays, which originates from Mn ions in different environments. The emitting rate of the (MnT1)-T-4((4)G) emission before 10 mu s is coarsely constant, which gives a robust confirmation that the ns-scale fast PL decay component in historical controversy is not from the (MnT1)-T-4((4)G) peak. With increasing temperature, both the ultrafast defects emission and the exciton emission attenuate, while the (MnT1)-T-4((4)G) emission enhances. This is attributed to the enhanced energy/charge transfer from the exciton and the ultrafast defects states to Mn ions. These findings can give insights on the electronic structure, energy/charge transfer processes of this kind of material.

Automated summary

Time-resolved photoluminescence experiments were conducted on MnS/ZnS core/shell quantum dots under high pressure and low temperature conditions. Different emission components were observed and discussed, with exciton emission showing a blue shift with increasing pressure. Furthermore, an enhancement in (MnT1)-T-4((4)G) emission was observed as temperature increased, which was attributed to enhanced energy/charge transfer processes from exciton and ultrafast defects states to Mn ions. This study provides insights into the electronic structure and energy/charge transfer processes of this type of material.