High-performance room-temperature ammonia sensors based on MAPb(I_1 - xBr_x)₃ perovskite films: a combined experimental...

A novel gas sensor based on CH₃NH₃Pb(I_1 - xBr_x)₃ (MAPb(I_1 - xBr_x)₃) perovskite materials was prepared to achieve the detection of NH₃ gas at room temperature of 25℃. The TiO₂ nanorod arrays were first synthesized on FTO glass through the hydrothermal method, and then MAPb(I_1 - xBr_x)₃ perovskite films were fabricated using a one-step spin-coating technique. Following Br doping, the morphology of the MAPb(I_1 - xBr_x)₃ perovskite film transitions from a dendritic to a tubular structure, leading to enhanced film quality and crystallinity. The gas-sensing test results demonstrate that the response of the MAPb(I_0.85Br_0.15)₃ sensor to 100 ppm ammonia is 36.8%, which is 1.9 times higher than that of the MAPbI₃ sensor at room temperature. The adsorption energy of MAPb(I_1 - xBr_x)₃ on ammonia was calculated through first-principles calculations. The results indicated that Br ions doping could enhance the adsorption capacity of MAPb(I_1 - xBr_x)₃ to ammonia molecules. The adsorption of ammonia by the MAPb(I_1 - xBr_x)₃ sensor is primarily attributed to ammonia molecules entering the octahedral center of the perovskite crystal, where they replace the MA⁺ cations and form NH₄Pb(I_1 - xBr_x)₃·MA intermediate compounds through a weak interaction akin to a chemical bond.