Energy band engineering in CsXBr3(X = Ge, Sn)/Janus MoSSe heterojunctions for photovoltaic applications

Abstract

Perovskite-based materials enable the stacking of different components through van der Waals (vdW) interactions, offering unprecedented flexibility in designing functional materials. By integrating perovskite CsXBr₃, (X = Ge, Sn) with two-dimensional transition metal dichalcogenides (TMDs) to form heterojunctions, synergistic effects are achieved, significantly enhancing the performance of optoelectronic devices. Using first-principles calculations based on density functional theory, we systematically investigate the electronic structure, interfacial charge transfer, and optical properties. The electronic structure of perovskite and MoSSe is preserved after heterojunction formation, and both type-I and type-II band alignments are attainable depending on the contact configuration, catering to different applications. Furthermore, charge accumulation near the interface generates an internal electric field that facilitates electron–hole separation. The formation of the heterojunction not only broadens and enhances the perovskite's light-absorption spectrum but, under strain modulation, the type-II configuration exhibits a theoretical power conversion efficiency (PCE) of up to 33.4% under idealized conditions based on the Scharber model. These findings unveil the interfacial characteristics of CsXBr₃/MoSSe heterostructures and highlight their potential for advanced optoelectronic applications.