Comparative study on the intrinsic NO2 gas sensing capability of triarylamine-based amorphous organic semiconductors

Abstract

In this study, three triarylamine derivatives (TPCAs) were designed to investigate the NO2 detection capability of amorphous organic semiconductors (OSCs). The TPCAs exhibited pure amorphous characteristics with nominal differences in molecular packing, but TPCA3M with three methoxy groups exhibited the highest sensitivity when confirmed with both fluorometric and field-effect transistor (FET)-based amperometric approaches. The associated NO2 detection capability was identified with the formation of TPCA-NO2 complex governed by the degree of charge transfer (CT) between electron donating TPCAs and electron accepting NO2. In addition, it was demonstrated, using a FET-based gas sensor with a patterned active layer, that the degree of NO2 diffusion is affected by molecular packing, which partly contributes to a high NO2 detection sensitivity of TPCA3M. In addition, the slow response and recovery characteristics reveals the limitation of TPCA-based FET as a practical NO2 sensor application, but the notable correlation between the structure and sensing capability in TCPAs provides informative material design strategies to improve the sensitivity of NO2 detection.