Optical alignment and orientation of excitons in ensemble of core/shell CdSe/CdS colloidal nanoplatelets

TL;DR

This study combines experimental measurements and theoretical modeling to analyze optical alignment and orientation of excitons in CdSe/CdS nanoplatelets, revealing insights into exciton dynamics and enabling spectral component identification.

Contribution

It introduces a comprehensive model accounting for bright and dark excitons in randomly oriented nanoplatelets, advancing understanding of exciton behavior in these nanostructures.

Findings

Determined parameters of bright and dark excitons.

Identified exciton and trion contributions via optical alignment.

Provided a method to analyze exciton dynamics without spectral resolution.

Abstract

We report on the experimental and theoretical studies of optical alignment and optical orientation effects in an ensemble of core/shell CdSe/CdS colloidal nanoplatelets. The dependences of three Stokes parameters on the magnetic field applied in the Faraday geometry are measured under continuous wave resonant excitation of the exciton photoluminescence. Theoretical model is developed to take into account both bright and dark exciton states in the case of strong electron and hole exchange interaction and random in-plane orientation of the nanoplatelets in ensemble. The data analysis allows us to estimate the time and energy parameters of the bright and dark excitons. The optical alignment effect enables identification of the exciton and trion contributions to the photoluminescence spectrum even in the absence of a clear spectral line resolution.