Abstract
When a UV photon is absorbed by a single semiconductor nanocrystal (NC), two or more excitons can be simultaneously generated through the carrier multiplication (CM) process. It is still highly debated whether the CM efficiency is truly enhanced in semiconductor NCs because all the routine CM measurements performed exclusively at the ensemble level are incapable of completely excluding the false CM signals contributed by the charged excitons. Here we place single CdSe NCs above an aluminum film and successfully resolve their UV-excited photoluminescence time trajectories where the true and false CM signals are contained in the blinking “on” and “off” levels, respectively. When the UV photon energy is ~2.46 times of the NC energy gap, an average CM efficiency of ~20.2% can be reliably estimated. The ability to detect UV-excited photoluminescence from a single NC will surely provide a great guidance for the CM applications in various light-to-electric conversion devices.
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