Ambient Stable CsCu₂I₃ Flexible Gas Sensors for Reliable NO₂ Detection at Room Temperature

The advancement of the Internet of Things and artificial intelligence has increased the demand for air quality monitoring to protect human health. Nitrogen dioxide (NO₂), a hazardous pollutant, causes inflammatory responses, even at low concentrations, necessitating sensitive gas sensors. Although metal oxide semiconductor sensors are commonly used, their high-operating temperature and reliance on additional heaters limit miniaturization and increase power consumption. Here, a lead-free, transparent, and flexible CsCu₂I₃ halide perovskite gas sensor was developed, demonstrating high sensitivity (1509% to 5 ppm) and selectivity for NO₂ detection at room temperature with full recovery. The sensor exhibited high stability in ambient air and high-humidity environments, which is not achievable with traditional halide perovskite sensors. First-principles density functional theory calculations revealed the mechanisms underlying its stability and sensitivity. This study highlights the potential of halide perovskites for low-power gas sensing at room temperature, addressing critical challenges for commercially viable wearable applications.