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.