Elementary Exciton Processes of InP/ZnS Quantum Dots Under Applied Pressure

In colloidal quantum dots (QDs), excitons are confined within nanoscale dimensions, and the relaxation of hot electrons occurs through Auger cooling. The behavior of hot electrons is evident under ambient pressure. Nanocrystal characteristics, including their size, are key to determining hot electron behavior because they serve as the stage. Applying pressure to materials can effectively modify this stage by providing a means to reversibly control interatomic distances. Unlike the behavior in ambient conditions, the pressure-dependent behavior remains unclear. In this study, InP/ZnS QDs were synthesized, and their pressure-dependent ultrafast carrier dynamics were analyzed using fs-transient absorption spectroscopy. The hot electron relaxation remained nearly constant with pressure up to 3 GPa, suggesting constant interaction between electrons and holes. However, above this threshold, the hot electron relaxation was accelerated by trapping from higher excited states. This study contributes to establishing a fundamental understanding of the pressure-dependent behavior of hot electrons in QDs.