ZnO/CuI Heterojunction UV‐Photovoltaic Gas Sensor for Self‐Powered IoT‐Integrated n‐Butylamine VOC Detection

Abstract The increasing demand for low‐power, compact, and efficient gas sensors for next‐generation technologies like Internet of things (IoT) platforms and portable devices drives the advancements in self‐powered gas sensing systems. Photovoltaic self‐powered sensors have emerged as a promising solution, harvesting light energy without external power. However, existing designs are limited by complex fabrication processes and a focus on oxidizing gases, which leaves behind reducing gases, particularly the volatile organic compounds (VOCs). This study presents a transparent, solution‐processed ZnO/CuI heterojunction‐based UV light‐induced photovoltaic self‐powered (UV‐PSP) gas sensor for the selective detection of VOC n‐butylamine. The sensor exhibits good sensitivity (0.0709), detection limit (6.6 ppm), and response (10% at 25 ppm). The ZnO/CuI heterojunction provides high electron mobility, chemical stability, and hydrophobicity, ensuring robust real‐time monitoring. The sensor also demonstrates long‐term stability (>80% response retention over 25 days) and reduced humidity interference. The sensing mechanism is investigated via Scanning Kelvin Probe to reveal the charge transfer dynamics. A functional IoT‐enabled prototype further validates its practical applicability for environmental and industrial applications, offering continuous and remote gas monitoring. This study establishes the ZnO/CuI heterojunction as a versatile and energy‐efficient platform for VOC detection for sustainable and portable sensor systems.