Magnetic circular polarization of photoluminescence of an inhomogeneous ensemble of colloidal nanocrystals

Abstract

In this paper, we theoretically analyze the recombination and spin dynamics of excitons in an inhomogeneous ensemble of colloidal nanocrystals, which consists of several subensembles with different lifetimes and degrees of circular polarization of exciton photoluminescence (DCP). Each subensemble is described within a three-level model of interacting exciton states, including two excited states and a ground state. Various ratios of parameters, leading to a nontrivial time-dependent DCP and a difference in the integral and equilibrium DCP characteristics, are considered. It is shown that the presence of subensembles with different polarizations and lifetimes results in nonmonotonic dependence and a change in the sign of the DCP in magnetic field and as a function of time can occur. The theoretical model was implemented to describe the time dependences of the DCP in ensembles of colloidal CdSe nanoplatelets synthesized in the air and argon atmosphere.