Iodine and Sulfur Vacancy Cooperation Promotes Ultrafast Charge Extraction at MAPbI3/MoS2 Interface

It is crucial to optimize hole transport materials (HTMs) to improve the performance of metal halide perovskites solar cells. While atomically thin two-dimensional transition metal chalcogenides (TMDs) are promising HTM candidates because of their high charge mobility, the nature of the formed type I heterojunction hampers the transfer of photoexcited holes. We show that a small concentration of sulfur vacancies (SV) is already sufficient to stabilize iodine vacancies (IV) at the MAPbI3/MoS2 interface (SV-to-IV process), to induce an interface dipole moment, and to reverse the offset of the valence band maxima, thus leading to ultrafast hole transport from the absorber to the electrode. The 0.2–0.8 ps time scale computed from nonadiabatic density functional theory is in agreement with experiment. Our results prove that the "SV-to-IV" interface vacancy engineering plays the crucial role in improving the HTM performance of TMDs.