Probing the Stability and Degradation of 2D Perovskites Using In Situ Infrared Spectroscopy

Metal halide perovskites are a promising class of opto-electronic materials due to their scalability, low cost, and high tunability. In as little as 7 years, the efficiency of single junction perovskite photovoltaics increased from 4% to 22%. Unfortunately, such perovskite materials readily degrade when exposed to ambient conditions (e.g., humidity and oxygen). Two-dimensional (2D) perovskites, which utilize large cation species to yield alternating layers of metal halide sheets and cations, demonstrate enhanced stability under ambient conditions compared to traditional bulk (3D) perovskites. Understanding why the layered 2D perovskite structure dramatically increases environmental stability may be the key to unlocking stable, highly-efficient perovskite photovoltaics.<br/>This work probes the decomposition mechanisms of two 2D perovskite materials synthesized with different sized “spacer” cations (butylammonium and phenethylammonium). We investigated the surface interaction with common environmental components, such as humidity and oxygen, using in situ infrared reflection-absorption spectroscopy with a custom designed chamber that enables precise control of the surrounding environment and temperature while directly probing the perovskite surfaces for changes to the local chemical environment.