Atmospheric\nExposure Triggers Light-Induced Degradation\nin 2D Lead-Halide Perovskites

Quasi-2D perovskites have been pivotal in recent efforts\nto stabilize\nperovskite solar cells. Despite the stability boost provided when\n these materials are introduced in perovskite solar cells, little\nis known about the intrinsic light and environmental stability of\nquasi-2D perovskites. In this study, we characterize the photostability\nof exfoliated quasi-2D perovskite single crystals in air using photoluminescence,\ninfrared, X-ray fluorescence, and energy-dispersive X-ray spectroscopy.\nPhotoexcitation leads to severe material loss with oxygen as a prerequisite\nfor material breakdown. The effect can be traced to the formation\nof reactive oxygen species, as demonstrated by increases in the photostability\nunder oxygen-free conditions. We show the effect of combined passivation\nsteps, showcasing the stability enhancement offered by 2D-capping\nlayers in combination with an oxygen-free atmosphere. Our results\nreveal that the stability of illuminated quasi-2D perovskites depends\ncritically on oxygen exposure, highlighting the importance of oxygen-blocking\npassivation strategies for stable 2D perovskite-based devices.