Synthesis and high ammonia gas sensitivity of (CH3NH3)PbBr3-xIx perovskite thin film at room temperature

Abstract A new organic inorganic hybrid perovskite material of MAPbBr3-xIx has been synthesized via a simple one step spinning method. The crystal structure, microstructure and surface morphologies, surface physic-chemical state were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy dispersion spectrum (EDS), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Meanwhile, ammonia, ethanol and acetone sensing tests were evaluated at room temperature of 15°C and the results show favourable response and selectivity towards ammonia. The gas sensing mechanism of MAPbBr3-xIx perovskite based sensor is also discussed. In ammonia gas sensing process, the adsorption, cation exchange and the reversible weak bonding between MA+ and NH4+ dominate the response and recovery processes. Furthermore, long time and high concentration ammonia gas exposure might accelerate the irreversible decomposition of MAPbBr3-xIx perovskite, which results in a decline in response value. To acetone and ethanol gases, the physical reversible tranfer of electrons from gas molecules to intrinsic bromide vacancies and uncoordinated Pb2+ cations in MAPbBr3-xIx perovskite might be the core of the gas sensing process, which results in short response-recovery time (less than 20 s), good repeatability, stability in wider range of gas concentration.