Highly Sensitive Photoinduced Carbon Dioxide Sensors Made by ZIF-67/Cs 2 AgBiBr 6 Heterojunction

Abstract

Carbon dioxide (CO2 ) emissions have become a key environmental issue of widespread concern at present. Currently, the use of metal oxide based chem-resistive gas sensors are restricted due to their high operating temperature and short lifetime. Therefore, the development of efficient and rapid gas sensors are of great significance in modern research. Lead free double perovskite, Cs2AgBiBr6 (CABB), could be activated by ultraviolet light and generate a large number of free carriers, which have the potential to increase charge density and enhance the gas sensitivity. Photoinduced carriers provide sufficient reactants, which contributes to the activation between target gases and sensitive semiconductors. Heterojunction of ZIF-67/CABB combines gas adsorption by ZIF-67 and photo-activated gas sensitive response by CABB in one device, which response could reach up to -95.55% when illuminated with the light of 365 nm wavelength and 17.34 mW cm -2 incident power density. Average response/recovery time of ZIF-67/CABB heterojunction could reach to 39.07s and 5.04s under UV illumination. The adequate response/recovery time of this fabricated device is 38.89s and 3.17s, with maximum response when at the voltage bias of 5V, which attains the advanced level comparable with commercially available CO2 detectors. The heterojunction system decreases the dark current density from 3.89 A m -2 to 0.78 A m -2 , and also decrease the light current density from 18.48 A m -2 to 5.33 A m -2 compared with pristine CABB at 5 V bias through current-voltage characteristic curves, which promotes the response and stability of the device. The linear dynamic range of the heterojunction gas sensor is 1700ppm-14000ppm, with sensitivity of 0.0013%/ppm. After more than 35 mins continuous stably work, the current density still remains consistent. This efficient, wide working voltage range and stable device presents the future of high-performance photo induced gas detector applications.