Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry–mass spectrometry analysis

Abstract

Thermal gravimetric and differential thermal analysis (TG-DTA) coupled with quadrupole mass spectrometry (MS) and first principles calculations were employed to elucidate the chemical nature of released gases during the thermal decomposition of CH₃NH₃PbI₃. In contrast to the common wisdom that CH₃NH₃PbI₃ is decomposed into CH₃NH₂ and HI, the major gases were methyliodide (CH₃I) and ammonia (NH₃). We anticipate that our findings will provide new insights into further formulations of the perovskite active material and device design that can prevent methylammonium decomposition and thus increase the long-term stability of perovskite-based optoelectronic devices.