X-ray photoelectron spectroscopy (XPS) has been used to investigate the composition of perovskite films upon exposure to different environmental factors, such as moisture, heat, and UV light. However, few research studies have determined that the X-ray itself could cause damage to the perovskite crystals. In this study, the X-ray-induced degradation of CH3NH3PbI3 perovskite films was investigated via XPS within an in situ ultrahigh vacuum system. It is demonstrated that fresh methylammonium lead iodine contains Pb2+ without the initial existence of Pb0. The Pb0 signal was discovered after a few hours of soft X-ray exposure, which indicates that the CH3NH3PbI3 perovskite structure undergoes a decomposition process to form metallic Pb. In addition, the nitrogen content was found to be significantly decreasing in the first hour of X-ray exposure. The discovery of the X-ray-induced chemical state change and the volatile methylamine of perovskite crystals could be further applied as an indicator for the field of X-ray sensors or detectors.

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Solution‐processable hole‐transporting materials are demonstrated to improve the performance of nonfullerene‐based organic photovoltaic devices in an inverted structure. A vanadium oxide (VOX) precursor, used as a sol–gel, is mixed with commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to form a well‐dispersed VOX:PEDOT:PSS solution. The work function and molecular distribution of the VOX:PEDOT:PSS thin film are examined by ultraviolet photoelectron spectroscopy (UPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), respectively. Unlike conventional PEDOT:PSS, VOX:PEDOT:PSS not only is compatible with highly hydrophobic photoactive layers but also aligns well with the highest occupied molecular orbital (HOMO) level of the polymer donor, reaching a power conversion efficiency of 10% (≈100% boost) and achieving an excellent device stability.