Co-Actions of Ambient Pressure and Gas Molecular Adsorption on the Carriers’ Transport in Polycrystalline Pentacene Thin-Film Transistors

Abstract

Organic transistors have proved to have potential applications in pressure sensors. However, few reports consider the coactions of pressure and ambient gas adsorption on the characteristics of the sensitive transistors. In this article, pentacene polycrystalline thin films were fabricated as the active layer of organic transistors, and the effects of ambient pressure and the gas adsorption on the carriers’ transport characteristics have been investigated. It was found that during the process from one atmosphere to vacuum (∼5 × 10–3 Pa) the device output, saturation source-drain currents (IDS), changed with pressure not monotonously but with an unexpected reversible minimum peak. Considering the variation of gas adsorption quantity and the distance between pentacene grains with pressure, we established models to understand the nature of the pressure sensitivity. We found that in low pressures the adsorption of gas molecules in grain boundaries was the main factor that affects device performance, whereas in high pressures, the shortening of the distance between pentacene grains was the main factor. Our research will benefit the understanding of charge-transport nature and, more importantly, give some instructions on using and designing highly sensitive pressure sensors.