Charge carrier coherence and Hall effect in organic semiconductors

摘要

Hall effect measurements are important for elucidating the fundamental chargetransport mechanisms and intrinsic mobility in organic semiconductors. However,Hall effect studies frequently reveal an unconventional behavior that cannot bereadily explained with the simple band-semiconductor Hall effect model. Here,we develop an analytical model of Hall effect in organic field-effecttransistors in a regime of coexisting band and hopping carriers. The model,which is supported by the experiments, is based on a partial Hall voltagecompensation effect, occurring because hopping carriers respond to thetransverse Hall electric field and drift in the direction opposite to theLorentz force acting on band carriers. We show that this can lead in particularto an underdeveloped Hall effect observed in organic semiconductors withsubstantial off-diagonal thermal disorder. Our model explains the main featuresof Hall effect in a variety of organic semiconductors and provides ananalytical description of Hall mobility, carrier density and carrier coherencefactor.