The Adsorption Postures of Water on CH3NH3PbI3 Surfaces: a First-Principles Insight

Abstract Inorganic organic perovskite solar cells (PSCs) are a kind of solar cells with rapid development in recent years, but their poor environmental stability, such as the water degradation behavior, hinders their commercialization. Here, we have thoroughly studied the adsorption postures of water on CH3NH3PbI3 surfaces. It is found that the adsorption energy of water molecules on perovskite surfaces is [-0.63, -0.59] eV, and with different initial postures, water molecules could eventually be adsorbed above Pb atom in a horizontal structure. The interaction between the perovskite surface and water molecules mainly comes from the electron exchange of Pb-O atoms. The weak interaction between H-I atoms makes the H atom approach the I atom, which could help maintain a horizontal structure of water molecules. The interactions between perovskite surfaces and water are well explained by our DFT calculations.