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 Mn4T1(4G) orange emission. With increasing pressure, the exciton emission shows blue shift as the band gap increases. The Mn4T1(4G) emission has different pressure shift rates at different time delays, which originates from Mn ions in different environments. The emitting rate of the Mn4T1(4G) emission before 10 μs is coarsely constant, which gives a robust confirmation that the ns-scale fast PL decay component in historical controversy is not from the Mn4T1(4G) peak. With increasing temperature, both the ultrafast defects emission and the exciton emission attenuate, while the Mn4T1(4G) 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.

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