Temperature-dependent ambipolar electrical characteristics of pentacene-based thin-film transistors: The impact of opposite-sign charge carriers

Abstract

The temperature-dependent electrical and charge transport characteristics of pentacene-based ambipolar thin-film transistors (TFTs) were investigated at temperatures ranging from 77K to 300K. At room temperature (RT), the pentacene-based TFTs exhibit balanced and high charge mobility with electron (μe) and hole (μh) mobilities, both at about 1.6cm2/Vs. However, at lower temperatures, higher switch-on voltage of n-channel operations, almost absent n-channel characteristics, and strong temperature dependence of μe indicated that electrons were more difficult to release from opposite-signed carriers than that of holes. We observed that μe and μh both followed an Arrhenius-type temperature dependence and exhibited two regimes with a transition temperature at approximately 210–230K. At high temperatures, data were explained by a model in which charge transport was limited by a dual-carrier release and recombination process, which is an electric field-assisted thermal-activated procedure. At T<210K, the observed activation energy is in agreement with unipolar pentacene-based TFTs, suggesting a common multiple trapping and release process-dominated mechanism. Different temperature-induced characteristics between n- and p-channel operations are outlined, thereby providing important insights into the complexity of observing efficient electron transport in comparison with the hole of ambipolar TFTs.