Fully radiative relaxation of silicon nanocrystals in colloidal ensemble revealed by advanced treatment of decay kinetics
Abstract
A comprehensive study of the spectrally resolved photoluminescence (PL) decay kinetics of dodecyl-passivated colloidal silicon nanocrystals (Si NCs) is presented. The correct treatment of average decay lifetime is demonstrated.
We report on importance to distinguish the external quantum efficiency (QE) from the internal QE. The external QE of the ensemble of Si NCs is measured to be similar to 60%, while the internal QE of Si NCs emitting around similar to 1.5 eV is evaluated to be near unity.
This difference between internal and external QE is attributed to a fraction of "dark" (absorbing but non-emitting) Si NCs in the ensemble. This conclusion is based on the analysis of deconvoluted size-selected decay curves retrieved by the presented mathematical procedure.
The homogeneous line-broadening is estimated to be around 180 meV by experimentally challenging single-NC PL measurements. In addition, radiative lifetimes are calculated by the envelope function approximation and confirm the observed exponential increase of lifetime with decreasing emission photon energy.
Published by AIP Publishing.