Unraveling atomic-scale origins of interfacial properties in CsPbBr3/M2O5 (M = Nb, Ta) heterojunctions: a combined first-principles and experimental approach.

We study the interface properties of CsPbBr₃/Nb₂O₅ and CsPbBr₃/Ta₂O₅ heterojunctions for structural, electronic, and optical characteristics. First-principles calculations were performed to analyze interfacial binding energy, electronic local function (ELF), charge density difference, and electrostatic potential. Four interface configurations were constructed based on CsPbBr₃ (100) and M₂O₅ (001) terminations, revealing that the PbBr/TaO interface exhibits the highest binding energy (0.0073 eV Å^-2), indicating superior stability. Charge transfer calculations demonstrate electron migration from CsPbBr₃ to M₂O₅, forming an internal electric field that promotes charge separation. ELF and charge density difference maps highlight strong covalent interactions at the interfaces, particularly in the PbBr/TaO interface. Experimental characterization via XRD, SEM, TEM and XPS confirms successful heterojunction formation with preserved crystallinity. These findings provide theoretical and experimental insights into optimizing M₂O₅-based electron transport layers to enhance PSC efficiency and stability.