Water-resistance of macromolecules adsorbed on CH₃NH₃PbI₃ surfaces: A first-principles study

Encapsulation within resin films is a promising approach for isolating perovskite materials from water. To gain fundamental insight into these systems, we performed first-principles calculations of macromolecule (polymerized siloxane; epoxy cured by phthalic anhydride; graphene sheet) coatings for the waterproofing of methylammonium lead iodide perovskite (MAPbI₃) surfaces. Our calculations reveal that alternating attractive/resistant functional groups on the siloxane- or epoxy-modified MAPbI₃ surfaces hinder the water diffusion process. Moreover, we examined a no-defect graphene sheet for its ability to isolate MAPbI₃ from water molecules. The hydrophobicity of the graphene resulted in water molecules forming clusters, rather than dispersing, upon the sheet.