Charge Transport Model Based on Single-Layered Grains and Grain Boundaries for Polycrystalline Pentacene Thin-Film Transistors

Abstract

The charge transport process in organic thin-film transistors (OTFTs) has always been under intensive research while the mechanism is still controversial, even in the small-molecule OTFTs. In this study, we report on a transport model for interpreting the charge transport mechanism in polycrystalline pentacene TFTs. By investigating the growth mode of pentacene films and the distribution of charge carriers in the channel of OTFTs, a transport model involving two-dimensional single-layered grains and grain boundaries (GBs), namely the two-dimensional grain boundary (TDGB) model, is proposed for describing the charge transport process in polycrystalline pentacene TFTs. An analytical expression for the field-effect mobility could be obtained from the model. The model is applied to explain the mobility dependence on the grain sizes at the first monolayer of pentacene films, temperature and on gate voltage in polycrystalline pentacene TFTs, with good agreement obtained. In addition, the values of some crucial parameters are given by the simulations based on the model.