Physical model of Seebeck coefficient under surface dipole effect in organic thin-film transistors

•Physical model of Seebeck coefficient was proposed based on VRH theory.•Surface dipole induced Seebeck effect in OTFTs was discussed.•Gate-voltage and temperature dependence of Seebeck effect are enhanced by a dipole.•Energetic disorder exhibits a weak dependent nature of Seebeck effect.

The surface dipole effect can play an important role in the performance of charge carrier transport in organic thin-film transistors (OTFTs). In this work, we propose a physical model of Seebeck coefficient based on variable-range hopping theory in OTFTs to characterize carrier thermoelectric transport. The model effectively explains the influence of a dipole on the carrier density, energetic disorder and temperature dependence of the Seebeck effect. The gate-voltage and temperature dependence of the Seebeck effect are remarkably enhanced by a dipole, while the energetic disorder exhibits a weak dependent nature. The Seebeck coefficients calculated in this study and those obtained experimentally in a previous study were found to be in good agreement.

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