Microstructure control of organic semiconductors via UV-ozone for high-sensitivity NO2 detection

Developing high sensitive organic semiconductors (OSCs) in organic thin-film transistors (OTFTs) is the key for OTFT based gas sensors. Herein, we report a simple processing route of highly sensitive OSCs for high performance OTFT based nitrogen dioxide (NO 2 ) sensors, where the active OSC layer is based on ultraviolet-ozone (UVO) treated poly(3-hexylthiophene-2,5-diyl) (P3HT). Compared to conventional P3HT based OTFT sensors, the reported device exhibits a remarkable improvement of the gas response from 350% to 30000%. The studies in morphologies, chemical compositions and microstructures of the UVO-treated films reveal that a large number of carrier traps generated in the P3HT films is the decisive reason for the enhancement of sensing performance. Moreover, the optimized device shows great potential of practical applications on the stand points of sensitivity, selectivity, reusability and the ability of recovery, as well as limit of detection of ~7.3 ppb. This simple method provides an innovative understanding for the role of the carrier traps in sensing performance and demonstrates a bright future for developing high performance OTFT gas sensors.