Atomic-Scale Insights into Termination-Dependent Interfacial Electronic Properties and Charge Transfer at MAPbI3/Rare-Earth Oxide (CeO2, La2O3) Heterojunctions

Abstract This study combines first-principles calculations with experimental investigations to elucidate the interfacial mechanisms of heterojunctions formed between MAPbI3 and rare-earth oxides (CeO2 and La2O3). For the MAPbI3/CeO2 and MAPbI3/La2O3 systems, four interfacial configurations were considered, yielding eight interfaces in total. All interfaces exhibit positive adhesion energies, indicating favorable structural stability. Compared with the MAI-terminated surface, the PbI-terminated surface exhibits stronger interfacial interactions, with the OLa–PbI interface showing the strongest binding. Interfacial charge redistribution reveals net electron transfer from the MAPbI3 layer to the rare-earth oxide layer across the interface. The potential drop, planar electrostatic potential, work function, and density of states at these interfaces are strongly influenced by the rare-earth oxide surface termination, with more pronounced effects in the MAPbI3/La2O3 heterojunction. The optical properties are dominated by the perovskite layer, while the rare-earth oxides further enhance the overall performance through polarization effects. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements confirmed the successful fabrication and structural stability of the heterojunctions, in good agreement with the computational predictions. This work offers fundamental understanding of the design of perovskite/rare-earth oxide interfaces and contributes to advancing high-performance perovskite-based optoelectronic devices.