Revisiting the thermal decomposition mechanism of MAPbI 3 .

The thermal stability of MAPbI 3 poses a challenge for the industry. To overcome this limitation, a thorough investigation of MAPbI 3 is necessary. In this work, thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy were conducted to identify the thermal decomposition products of MAPbI 3 , which were found to be CH 3 I, NH 3 , and PbI 2 . 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 MAPbI 3 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 MAPbI 3 , providing valuable theoretical support for the design of long-term stable devices.