Frequency-dependent spontaneous emission rate from CdSe and CdTe nanocrystals: influence of dark states

TL;DR

This study investigates how the spontaneous emission rate in CdSe and CdTe nanocrystals varies with emission frequency, highlighting the role of dark exciton states and thermal effects at room temperature.

Contribution

It provides experimental and theoretical analysis of frequency-dependent emission rates, emphasizing the influence of dark states on radiative processes in nanocrystals.

Findings

Emission rate increases supra-linearly with frequency.

Dark exciton states significantly attenuate emission rates.

Theoretical calculations align with experimental results.

Abstract

We studied the rate of spontaneous emission from colloidal CdSe and CdTe nanocrystals at room temperature. The decay rate, obtained from luminescence decay curves, increases with the emission frequency in a supra-linear way. This dependence is explained by the thermal occupation of dark exciton states at room temperature, giving rise to a strong attenuation of the rate of emission. The supra-linear dependence is in agreement with the results of tight-binding calculations.