Physical and chemical properties and degradation of MAPbBr films on transparent substrates

To date, the potential exploitation of hybrid organic-inorganic perovskites (HOIPs) in photovoltaic technologies has been significantly hampered by their poor environmental stability. HOIP degradation can be triggered by conventional operational environments, with excessive heating and exposure to oxygen and moisture significantly reducing the performances of HOIP-based solar cells. An imperative need emerges for a thorough investigation on the impact of these factors on the HOIP stability. In this work, the degradation of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) thin films, deposited via spin-coating on indium tin oxide (ITO) and strontium titanate (STO) substrates, was investigated by combining Raman and ultraviolet-visible (UV-Vis) absorption spectroscopy, as well as optical and fluorescence microscopy. We assessed the physical and chemical degradation of the films occurring under diverse preservation conditions, shedding light on the byproducts emerging from different degradation pathways and on the optimal HOIP preservation conditions. We explore the physical and chemical degradation mechanisms of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) thin films, depending on the storage conditions. We show that, under vacuum conditions, the NH 4 Pb 2 Br 5 degradation compound can be formed.