Exciton-Phonon Coupling in Single Band-Gap Engineered ZnCdSe-Dot/CdS-Rod Nanocrystals

Abstract

Exciton-phonon coupling limits the homogeneous emission linewidth of nanocrystals. Hence, a full understanding of it is crucial. In this work, we statistically investigate exciton-phonon coupling by performing single-particle spectroscopy on Zn$_{1-x}$Cd$_{x}$Se/CdS dot-in-rod nanocrystals at cryogenic temperatures ($T\approx 10~\rm{K}$). In situ cation exchange enables us to analyze different band alignments and thereby different charge-carrier distributions. We find that the relative intensities of the longitudinal optical S- and Se-type phonon replicas correlate with the charge-carrier distribution. Our experimental findings are complemented with quantum mechanical calculations within the effective mass approximation that hint at the relevance of surface charges.