Spectral and dynamical properties of multiexcitons in semiconductor nanorods†

Abstract

Multiple exciton dynamics in semiconductor nanocrystals is usually characterized by the observation of changes in the fast multiexponential kinetics at the band edge transition position in transient absorption spectroscopy at varying excitation intensities. However, analysis of this complex decay dynamics is not straightforward and complicated by varying initial distributions of multiple excitons of increasing order with increasing excitation intensity and the superposition of contributions from multiexciton processes and charge carrier trapping, which need to be distinguished. In this study, we not only analyse kinetics but also transient absorption spectra to identify characteristic spectroscopic signatures for the presence of multiple excitons of varying orders beyond biexcitons in seeded and non-seeded CdS nanorods. Applying an MCMC (Markov Chain Monte Carlo) sampling approach for global target analysis enables us to determine the contributions of multiple exciton decay via Auger recombination and the contribution of a potential population of surface exciton states to the observed decay dynamics.