Electronic transport within a quasi two-dimensional model for rubrene single-crystal field effect transistors

TL;DR

This study models charge transport in rubrene single-crystal transistors using a quasi-2D SSH model, revealing temperature-dependent mobility behavior consistent with experimental observations and emphasizing the role of localized states and anisotropy.

Contribution

It introduces a realistic high-dimensional quasi-2D model for rubrene transistors that accurately captures mobility and anisotropy without uncontrolled approximations.

Findings

Mobility scales as T^{-γ} with γ ≥ 2, matching experiments.

Transport lifetime is an order of magnitude shorter than spectral lifetime.

Mobility reaches the Ioffe-Regel limit at higher temperatures.

Abstract

Spectral and transport properties of the quasi two-dimensional adiabatic Su-Schrieffer-Heeger model are studied adjusting the parameters in order to model rubrene single-crystal field effect transistors with small but finite density of injected charge carriers. We show that, with increasing temperature $T$, the chemical potential moves into the tail of the density of states corresponding to localized states, but this is not enough to drive the system into an insulating state. The mobility along different crystallographic directions is calculated including vertex corrections which give rise to a transport lifetime one order of magnitude smaller than spectral lifetime of the states involved in the transport mechanism. With increasing temperature, the transport properties reach the Ioffe-Regel limit which is ascribed to less and less appreciable contribution of itinerant states to the conduction process. The model provides features of the mobility in close agreement with experiments: right order of magnitude, scaling as a power law $T^{-\gamma}$, with $\gamma$ close or larger than two, and correct anisotropy ratio between different in-plane directions. Due to a realistic high dimensional model, the results are not biased by uncontrolled approximations.