Polarons Explain Luminescence Behavior of Colloidal Quantum Dots at Low Temperature

TL;DR

This paper introduces a model explaining the luminescence behavior of colloidal quantum dots at low temperatures by considering exciton-phonon interactions, accounting for spectral features and decay dynamics.

Contribution

The model uniquely incorporates solid-state environment effects and predicts dressed states, explaining previously unexplained experimental observations.

Findings

Explains short photoluminescence lifetime

Accounts for zero-longitudinal optical phonon line

Describes temperature-dependent luminescence behavior

Abstract

Luminescence properties of colloidal quantum dots have found applications in imaging, light-sources, and displays. Despite wide interest, several experimental observations from these quantum dots, such as the short lifetime on the scale of microseconds and a zero-longitudinal optical phonon line in low-temperature photoluminescence spectrum, remain unexplained by existing models. Here we propose a model including the effect of solid-state environment on luminescence by capturing coherent and incoherent interactions of band-edge exciton with phonon modes. Our model predicts the formation of dressed states by coupling of the exciton with a confined acoustic phonon mode, and explains the short lifetime and the presence of the zero-longitudinal optical phonon line in the spectrum. Accounting for the interaction of the exciton with bulk phonon modes, the model also explains the experimentally observed temperature-dependence of the photoluminescence decay dynamics and temperature-dependence of the photoluminescence spectrum.