Charged excitons, Auger recombination and optical gain in CdSe/CdS nanocrystals

Abstract

CdSe/CdS colloidal nanocrystals are members of a novel class of light-emittingnanoparticles with remarkable optical properties such as suppressed fluorescence blinkingand enhanced emission from multiexciton states. These properties have been linked tothe suppression of non-radiative Auger recombination. In this work we employultrafast spectroscopy techniques to identify optical signatures of neutral andcharged excitonic and multiexcitonic states. We show that Auger recombination ofbiexcitons is not suppressed, while we observe optical gain and amplified spontaneousemission from multiexciton states and from long-lived charged-exciton states.