Extended storage of multiple excitons in trap states of semiconductor nanocrystals

Abstract

Owing to the Auger recombination effect, multiple excitons (MEs) in semiconductor nanocrystals (NCs) are dissipated nonradiatively at the sub-nanosecond time scale, which sets a stringent limit on the time window within which one can operate with them. Here, we show that this issue can be resolved by utilizing an intrinsic energy transfer system in CdSe NCs, where MEs created in the donor quantized states can be effectively extracted to the acceptor trap states. This was evidenced by the step-like increase in the intensity and the apparent decrease in the rise time of the trap-state photoluminescence with the elevated laser excitation power. With the radiative lifetime being tens of nanoseconds for the trap states, extended storage of MEs has been achieved and marks a crucial step towards flexible manipulations of their optoelectronic properties.