Subpicosecond near-infrared fluorescence upconversion study of relaxation processes in PbSe quantum dots

Abstract

We report on the (sub)picosecond relaxation processes in PbSe quantum dots of different sizes, measured by a near-infrared photoluminescence upconversion technique. The early-time spectra are characterized by emission from several low-lying excited states. The direct measurement of the Huang-Rhys factors of the lowest excited states excludes strong electron-phonon coupling in the intraband relaxation. The kinetics point to a fast sequential cascade process between excited states, governed by energy gaps and a quasicontinuous valence-band structure.