Control Strategies for Solution-Processed ZTO-Based Thin-Film Transistors Tailored Toward Volatile Organic Compound Detection

A breakthrough in the fabrication of amorphous Zn-Sn-O (ZTO)-based thin-film transistors (TFTs) is presented for volatile organic compound (VOC) detection. The incorporation of highly abundant materials offers substantial economic and environmental benefits. However, analyses for the design of a multilayer channel are still limited. This work demonstrates that the chemical environment influences ZTO-based TFTs' carrier transport properties and can be tailored for detecting specific VOCs, ensuring high specificity in diagnosing life-threatening conditions through simple breath analysis. A low-cost, high-throughput, fully solution-processed ZTO and ZnO multilayering strategy is adopted. The in-depth compositional and morphological analyses reveal that low surface roughness, excellent Zn and Sn intermixing, high oxygen vacancy (31.2%), and M-OH bonding (11.4%) contents may account for the outstanding electrical and sensing performance of ZTO-ZTO TFTs. Notably, these TFTs achieve near-zero threshold voltage (2.20 V), excellent switching properties (10⁷), and high mobility (10 cm²V⁻¹s⁻¹). This results in high responsivity to alcohol vapors at low-voltage operation with peak responsivity for methanol (R = 1.08 × 10⁶) over two orders of magnitude greater than acetone. When miniaturized, these devices serve as easy-to-operate sensors, capable of detecting VOCs with high specificity in ambient conditions.