Dipole Orientation Influences Electron Transfer and Carrier Recombination at CH3NH3PbI3/C60 Interface: A Time-Domain Ab Initio Study

Nonradiative recombination and energy-level mismatch at perovskite/fullerene interfaces limit inverted perovskite solar cells using C60 electron-transport layers, while extrinsic passivation suffers from process complexity and limited reproducibility. We exploit methylammonium (MA) dipole orientation in CH3NH3PbI3 (MAPbI3) together with iodine vacancies (VI) to electrostatically program charge-selective MAPbI3/C60 contacts. Time-domain density functional theory and ab initio nonadiabatic molecular dynamics across five configurations show that MA orientation alone imposes a kinetic trade-off: configurations favoring fast electron transfer suffer rapid recombination. VI breaks this constraint by introducing a geometrically distinct defect dipole. When antiparallel to the MA dipole at the NH3+-terminated interface, this dipole corrects the conduction-band offset, widens the interfacial gap, suppresses nonadiabatic coupling, and enriches interfacial electrons, yielding 2.08 ps electron transfer with a 2.09 ns carrier lifetime. The net interfacial dipole linearly predicts band alignment; hydrogen interstitials follow the same electrostatic mechanism, defining a transferable design principle beyond static passivation.