Colorimetric Vertically Stacked Sensor Array Enabled by Solution-Processed Oxide Semiconductors for Volatile Organic Compound Detection

This work demonstrates the synthesis of spin-on oxide semiconductors via an ultraviolet (UV)-assisted annealing process using metal–organic precursors with β-diketone ligands. This process promotes the decomposition and subsequent condensation while preserving a high density of hydrogen- and oxygen-related donor species. These donors effectively supply free electrons and fill shallow trap states near the conduction band minimum (CBM), resulting in enhanced carrier mobility and on-current. A peak field-effect mobility of 89 cm²/V·s, an on-current (I_on) of 26.42 μA, and an I_on/I_off ratio of 10⁸ were achieved in bottom-gated transistors using a SiO₂ gate dielectric. Moreover, the high density of trap states near the CBM broadens the spectral detection range from UV to visible light, yielding a high responsivity of 8,900 A/W and a detectivity of 1.26 × 10¹⁴ Jones. Leveraging this broadband photoresponsivity, we further developed a vertically stacked sensor platform for the detection of volatile organic compounds (VOCs). These results highlight UV-assisted solution processing as a powerful strategy to realize high-performance oxide electronics and multifunctional sensor platforms.