Highly Sensitive Gas Sensors Made by Copper‐Doped Double Perovskite for Carbon Dioxide Detection at Room Temperature

Environmental protection issues in industrial age have become an important topic of great concern worldwide. Effective greenhouse gas detectors have received significant attention in environmental‐monitoring. Semiconductor‐based gas sensors have broad prospects due to their simple preparation, convenient usage, and efficient response. Perovskite have emerged for carbon dioxide (CO 2 ) detectors owing to their adjustable semiconductor characteristics. Doping on perovskite as a functionalizing method for enhanced performance is proposed in this paper, aiming to fabricate highly sensitive sensors. Copper dopant could increase surface electron concentration, being conducive to the reaction between semiconductors and targeted gases. Semiconductor carrier concentration boost influenced by doping effect stems from energy‐band variation. Gas sensing experiments demonstrate that 15%‐molar Cu doping in Cs 2 AgBiBr 6 (CABB) has best mobility at 3.304 cm 2 V −1 s −1 and it could obtain the best film surface with smooth grains and great gas sensitive response, with a response of 21.11 at 5000 ppm CO 2 and 1.5 V bias. Furthermore, the highest sensitivity of CABB (15% Cu) based gas sensor is 0.464% ppm −1 , with a linear dynamic range of 1200–1700 ppm. The device exhibited operational stability under continuous repeated usage, ensuring long‐term reliability in standard environmental conditions. Average response/recovery times of these CO 2 sensors are 3.07/14.16 s, respectively, demonstrating strong potential for gas‐sensitive monitoring.