Polaron Transport in Organic Crystals: Temperature Tuning of Disorder Effects

TL;DR

This paper investigates how temperature influences polaron transport in disordered organic crystals, revealing a transition from localization effects to phonon-assisted mobility enhancement and downturns.

Contribution

It introduces a model capturing temperature-dependent polaron mobility in disordered organic crystals, highlighting the interplay of coherence and phonon scattering effects.

Findings

Weak localization at low temperatures in strong disorder

Mobility increases with temperature due to thermal disorder

Mobility downturn occurs at a transition temperature due to phonon scattering

Abstract

We explore polaronic quantum transport in three-dimensional models of disordered organic crystals with strong coupling between electronic and vibrational degrees of freedom. By studying the polaron dynamics in a static disorder environment, temperature dependent mobilities are extracted and found to exhibit different fingerprints depending on the strength of the disorder potential. At low temperatures and for strong enough disorder, coherence effects induce weak localization of polarons. These effects are reduced with increasing temperature (thermal disorder) resulting in mobility increase. However at a transition temperature, phonon-assisted contributions driven by polaron-phonon scattering prevail, provoking a downturn of the mobility. The results provide an alternative scenario to discuss controversial experimental features in molecular crystals.