Sub-ppm and high response organic thin-film transistor NO2 sensor based on nanofibrillar structured TIPS-pentacene

We investigated the effect of off-center spin coating process on the characteristics of organic thin-film transistors (OTFTs) based nitrogen dioxide (NO2) sensors. Different nanofibrillar structured directions were obtained through off-center spin coating which significantly improved the sensing property compared to that fabricated by the conventional on-center spin coating process. A remarkable enhancement of gas responsivity from 31.9% to 221.5% under 30 ppm NO2 was achieved by orthogonal off-center spin coating. While, device by parallel offcenter spin coating showed an excellent sensitivity of 44.3% under ppb-level NO2 (250 ppb), and the response under 1 ppm also exhibited 35-fold increase. After a comprehensive analysis on the morphology properties of the organic films and electrical properties of devices, it was revealed that the multiform performance improvement was largely related to the nanofibrillar structured organic semiconductor (OSC) films facilitated by off-center spin coating, leading to a well-regulated change of potential barriers at grain boundaries. Compared to the common strategies, this work develops a simple, efficient and reliable access to obtain high performance solution- processed OTFT based gas sensors.