Spin-Orbit Coupling Accelerates the Photoinduced Interfacial Electron Transfer in a Fullerene-Based Perovskite Heterojunction

In this work, we explore the interfacial properties of the C60-Py@MAPbI3 heterojunction of the PbI-terminated MAPbI3(001) surface and pyridine-functionalized C60-Py fullerene derivative through both collinear and noncollinear density functional theory calculations with and without spin-orbit coupling (SOC) effects. C60-Py is bound to the MAPbI3 surface through interfacial Pb-O and Pb-N bonds. Although C60-Py@MAPbI3 is predicted to be the same type II heterojunction at all of the computational levels considered, the SOC effects largely decrease the energy gap of the first conduction bands of C60-Py and MAPbI3, thereby accelerating the interfacial electron transfer. Further dynamics simulations show that the inclusion of the SOC effects induces the transfer of approximately 80% of electrons from MAPbI3 to C60-Py within 1 ps. The work demonstrates that the SOC effects are indispensable for the interfacial properties of C60-Py@MAPbI3 and could also play a non-negligible role in tuning the optoelectronic properties of fullerene-based or similar perovskite devices.