Unveiling the Degradation of Methylammonium Lead Iodide (MAPbI3) Perovskite under Simultaneous External Conditions

Metal halide perovskites have attracted significant attention for a broad range of optoelectronic and photonic applications due to their fascinating properties. Particularly, methylammonium lead iodide (MAPbI3) has shown specific promise for many applications, but its long-term stability remains a major challenge. This work systematically investigates the degradation pathway of MAPbI3 perovskite thin films under the combined effect of temperature (20–40 °C) and humidity (20–40%). We used a combination of advanced theoretical calculations and characterization tools to gain in-depth insight into the degradation mechanism of MAPbI3 perovskite. The findings reveal that increased temperature and humidity accelerate the decomposition of the perovskite structure, leading to the formation of degradation products such as PbI2, Pb(OH)I, and PbCO3. A clear trend in the degradation rate was observed, with the most severe degradation occurring under simultaneous high temperature and humidity. Quantitatively, under the maximum exposure condition (H40-T40), the MAPbI3 (110)/PbI2 (001) XRD intensity ratio dropped sharply from approximately 3.8 to near zero after 144 h. In contrast, under the H20-T20 condition, the ratio decreased gradually from 4.3 to 0.4 after a 240 h. These findings provide insights into the environmental degradation pathways of MAPbI3 thin films, highlighting the critical influence of temperature and humidity on their stability. Our computational calculations provide a molecular-level understanding of the mechanisms driving degradation.