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First-Principles Study of Zinc Phthalocyanine Molecules Adsorbed on Methylammonium Lead Iodide Surfaces

Energy level alignment between halide perovskites and charge transport layers plays a key role on charge extraction in perovskite solar cells. On the basis of density functional theory calculations, we have studied the interfacial structures and electronic properties of zinc phthalocyanine (ZnPc) adsorbed on methylammonium lead iodide (MAPbI3) (001) surfaces with face-on orientation. Both MAI- and PbI2-terminated surfaces have been considered. The calculated valence band maximum (VBM) and conduction band minimum (CBM) of the PbI2-terminated surface are lower than those of the MAI-terminated surface. The ZnPc/MAI interface shows type-I band alignment, while ZnPc/PbI2 exhibits type-II band alignment, which favors to the interface charge separation. The energy level shift is ascribed to the difference of work function between MAPbI3 slab and ZnPc molecule, which results in spontaneous charge transfer at the interface. Our result indicates that ZnPc is a suitable candidate as hole transport material for MAPbI...