Highly Sensitive OFET Based Room Temperature Operated Gas Sensors Using Thieno[3,2-b]thiophene Extended Phthalocyanine Semiconductor

Over the past decades, organic field-effect transistor (OFET) gas sensors have maintained a rapid development. However, the majority of OFET gas sensors show insufficient detection capability towards oxidizing and hazardous gases such as nitrogen dioxide (NO₂) and sulfide dioxide (SO₂). In this report, a sustainable approach toward fabrication of OFET gas sensor, consisting of thieno[3,2-b]thiophene (TT) and phthalocyanine (Pc) based electron rich structure (TT-Pc) for detection of both nitrogen dioxide (NO₂) and sulfide dioxide (SO₂) is disclosed for the first time. Khaya gum (KG), a natural, biodegradable biopolymer is used as the gate dielectric in these OFET-based sensors. Thin film properties and surface morphology of TT-Pc were investigated by UV-Vis, SEM, AFM and contact angle measurements, which indicated a uniform and smooth film formation. The UV-Vis properties were supported by computational chemistry, performed using density functional theory (DFT) for optimizing geometry and absorption of TT-Pc models. Sensitive and selective responses of 90% and 60% were obtained from TT-Pc OFET-based sensors upon exposure to 20 ppm of NO2 and SO₂, respectively, under ambient conditions. One of the lowest limits of detection of ~165 ppb was achieved for both NO₂ and SO₂ using solution-processed TT-Pc sensor with natural, biodegradable dielectric biopolymer. The sensors showed excellent long-term environmental and operational stability with only a 7% reduction of the sensor’s initial response (%) upon exposure to NO₂ and SO₂ over nine months of operation in air.