Fig. 2: Effects of humidity on layered perovskites.

Model of MAPbI₃/quasi-2D heterojunctions in contact with water (a) schematic of 3D MAPbI₃ film covered with PEA-based quasi-2D perovskite (n = 5) (b) illustration of disproportionation of n = 5 PEA-based perovskite into 3D perovskite MAPbI₃ and more stable n = 3 or n = 2 quasi-2D perovskites, with the loss of I⁻ ions indicated by violet circles and the loss of MA⁺ ions indicated by green circles illustrating the irreversible degradation of the 3D perovskite to volatile compounds and PbI₂. Reprinted with permission from ref. 27. Copyright 2019 American Chemical Society; Schematic representations of structural changes in Dion-Jacobson perovskite structure in the presence of water (c) the (PDMA)PbI₄ layered structure and d hydrated 1D (PDMA)Pb₂I₆·2H₂O structure. Reprinted with permission from ref. 30. Copyright 2021 American Chemical Society.