Interplay between electron-phonon couplings and disorder strength on the transport properties of organic semiconductors

TL;DR

This study explores how electron-phonon interactions and disorder influence charge transport in organic semiconductors, revealing their combined effects on mobility and polaron formation, with implications for device performance.

Contribution

It provides a comprehensive model including both bulk and interface electron-phonon couplings along with disorder, advancing understanding of transport mechanisms in organic semiconductors.

Findings

Disorder enhances activation energies of mobility.

Localized polarons form at lower electron-phonon couplings due to disorder.

Model aligns with experimental data on rubrene transistors.

Abstract

The combined effect of bulk and interface electron-phonon couplings on the transport properties is investigated in a model for organic semiconductors gated with polarizable dielectrics. While the bulk electron-phonon interaction affects the behavior of mobility in the coherent regime below room temperature, the interface coupling is dominant for the activated high $T$ contribution of localized polarons. In order to improve the description of the transport properties, the presence of disorder is needed in addition to electron-phonon couplings. The effects of a weak disorder largely enhance the activation energies of mobility and induce the small polaron formation at lower values of electron-phonon couplings in the experimentally relevant window $150 K<T<300 K$. The results are discussed in connection with experimental data of rubrene organic field-effect transistors.