Pressure-dependent Photoluminescence of CdSe/ZnS Quantum Dots: Critical Point of Different Pressure Regimes

High pressure condition can alter and control the electronic structure of semiconductor quantum dots, and therefore provides novel insight for designing optoelectronic devices. Here we report the pressure-dependent photoluminescence (PL) of CdSe/ZnS core/shell quantum dots (QD) in different pressure regimes. The center of the PL spectrum has blue-shift when hydrostatic pressure increases, due to the increasing bulk modulus. However, the shifting rate becomes lower in the higher pressure regime, i.e. above the critical pressure point, mainly due to the interaction between QDs. Accordingly, the lifetimes of PL drop in the low pressure regime, due to the increased pressure-induced trapping states, then increase above the critical pressure point, indicating the interaction between dots likewise. The observed critical pressures for both cases are consistent with each other, and strongly depend on the QD concentration, which forcefully support the aforementioned interaction model.