Design and engineering of bifunctional CuInO2 thin-film devices for integrated photodetection and CO gas sensing

In this study, the synthesis and characterization of bifunctional CuInO2 thin films that are sensitive to sunlight and can detect carbon monoxide (CO) gas were reported. CuInO2 films were synthesized on fluorine-doped tin oxide (FTO)-coated glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) method at 20, 30, and 40 SILAR cycles. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicated that the films were in pure hexagonal phase, in dense and uniform nanoplate morphology. UV-Vis analysis revealed that the films exhibited maximum transmittance between 55% and 63% in the visible wavelengths, along with a direct band gap energy ranging from 3.66 to 3.87 eV. The photosensitive behavior of the CuInO2 thin film-based sensors was analyzed in the solar irradiation range of 20–100 mW/cm2. The photodetection results indicated that the sensors exhibited high photosensitivity and fast response speed (τr: 0.6 s, τd: 0.4 s). Gas sensing measurements performed within the temperature range of 30 °C to 135 °C revealed that the sensors exhibited optimum performance at 90 °C. The sensors had high sensitivity, ranging from 2.9% to 65.3%, to CO gas concentrations between 0.1 ppm and 50 ppm, along with good selectivity, baseline stability, and stable repeatability. Moreover, the optimum response and recovery times of the sensors were found to be 32.8 s and 41.8 s for 50 ppm CO gas at 90 °C, respectively. Finally, CuInO2 thin film-based sensors offer excellent sensitivity, selectivity, and long-term stability, combined with a simple fabrication process, making them highly promising for industrial applications. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.