Charge carrier coherence and Hall effect in organic semiconductors

TL;DR

This paper presents an analytical model explaining the unconventional Hall effect in organic semiconductors, accounting for coexisting band and hopping carriers and their impact on charge transport measurements.

Contribution

It introduces a new analytical model that explains the Hall effect behavior in organic semiconductors with mixed charge carriers, supported by experimental validation.

Findings

The model explains underdeveloped Hall effects in disordered organic semiconductors.

It provides analytical expressions for Hall mobility, carrier density, and coherence factor.

Experimental data supports the model's predictions across various materials.

Abstract

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model explains the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.