Analysis of Multi-Gas Molecule Interactions in Ambient Air on Solution-Processed Indium Zinc Oxide Thin-Film Transistors for High-Performance Chemical Sensors

Unencapsulated solution-processed oxide-semiconductor transistors suffer from cross-sensitivity and baseline instability. In this study, we systematically investigate the field-effect transport kinetics and species-dependent gas interaction dynamics of solution-processed amorphous indium zinc oxide thin-film transistors across pressure state transitions (760–10−3 Torr) and single-gas purging environments (N2, O2, Ar, CO2, and humid air > 90% relative humidity). Our experimental findings indicate that atmospheric pressure variations dictate bulk channel conduction via free-carrier density shifts, whereas relative humidity drives parasitic gate (IG)/surface leakage currents (Isurface) through moisture-mediated interfacial trap creation. Purging tests reveal a nonpolar sensing window where N2 promotes bulk carrier accumulation, while Ar drives carrier depletion without degrading gate dielectric insulation. Electrophilic O2 suppresses channel current while increasing IG, whereas CO2 exhibits total electrical invariance. Real-time pulse-switching measurements confirm high detection fidelity (maximum signal-to-noise ratio > 30 dB for N2 and Ar) with excellent recovery. Correlating these dynamic responses with an exponential sub-bandgap density-of-states model establishes key principles for developing unencapsulated oxide chemical sensors that can discriminate complex gas–species mixtures in real-world ambient environments.