Revisiting the thermal decomposition mechanism of MAPbI₃

The thermal stability of MAPbI₃ poses a challenge for the industry. To overcome this limitation, a thorough investigation of MAPbI₃ is necessary. In this work, thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy were conducted to identify the thermal decomposition products of MAPbI₃, which were found to be CH₃I, NH₃, and PbI₂. In situ X-ray diffraction (XRD) measurements were then performed in the temperature range from 300 to 700 K, which revealed the significant decomposition of the (110), (220), and (310) surfaces of MAPbI₃ between 550 and 600 K. Density functional theory (DFT) calculations demonstrated that the (220) surface exhibited the highest stability. Additionally, the transition states of thermal decomposition showed that the energy barrier for the decomposition of the (110) surface was 2.07 eV. Our combined experimental and theoretical results provide a better understanding of the thermal decomposition mechanism of MAPbI₃, providing valuable theoretical support for the design of long-term stable devices.