Improving room-temperature ammonia sensing properties of CH3NH3PbI3-based gas sensors via coordination interaction using monoethanolamine ligand

Organic-inorganic hybrid perovskite materials have garnered significant research interest owing to their exceptional crystallographic characteristics and remarkable optoelectronic properties. This study presents a breakthrough in room-temperature ammonia sensing through the rational design of CH 3 NH 3 PbI 3 (MAPbI 3 )-based chemiresistive sensors modified with monoethanolamine (MEA) ligands. By integrating MEA as a coordination agent into the perovskite precursor solution, we achieved controlled crystallization dynamics, yielding compact MAPbI 3 films with unique maple-leaf grain morphology and enhanced humidity resistance. The optimized TiO 2 /MEA-MAPbI 3 sensor exhibited a nearly 2.1-fold improvement in response amplitude toward 100 ppm NH 3 compared to unmodified counterparts, alongside exceptional selectivity to NH 3 against interfering gases. Crucially, MEA-derived (PbI 2 )-MEA-(MAI) molecular shielding layers at grain boundaries suppressed moisture-induced degradation, enabling stable operation in air environment (∼30 %RH) with less than 22 % response degradation over 29 days. Mechanistic analyses revealed that the sensing behavior originates from reversible cation exchange between methylammonium (MA + ) and ammonium (NH 4 + ) species at the perovskite surface, corroborated by density functional theory (DFT) calculations showing preferential NH 3 adsorption over other analyte gases.