3D/2D lead-free halide perovskite CsSnBr3/MoX (X = Se2, SSe, S2) heterostructures for high-efficiency solar cell: Interface engineering strategies and transition of band alignments

• The CsSnBr 3 /MoX (X = Se 2 , SSe, S 2 ) vdW heterostructures were systematically studied using DFT. • Type I, II, and III transitions of energy band arrangements are achieved through interface engineering strategies to suit different applications. • The interface effect of the van der Waals heterojunction structure effectively enhances the optical absorption range and intensity. • The theoretically estimated PCE of the heterostructure thin-film solar cell reaches 21.4%. The rapid progress in the fabrication of van der Waals (vdW) heterostructures based on perovskite has significantly advanced the fields of optoelectronics and solar cells by integrating the exceptional properties of different materials. Overall, perovskite-based vdW heterostructures display unique functional characteristics due to their varied type-I, type-II, and type-III energy band configurations. However, it is a challenge to achieve flexible regulation of band edge alignment in heterostructures for different applications. Using first-principles density functional theory, we systematically study the electronic and optical properties of vdW heterostructures system consisting of three-dimensional lead-free all-inorganic halide perovskite materials CsSnBr 3 and MoX (X = Se 2 , SSe, S 2 ). The research results show that in the CsSnBr 3 /MoX vdW heterostructures, type I, II, and III transitions of band arrangements are achieved through interface engineering strategy to adapt to different applications. Meanwhile, by calculating the light absorption efficiency of the constructed 3D/2D vdW heterostructures, it was found that the interface effect enhances the optical absorption range and intensity of the perovskite-based heterostructures. The theoretically estimated power conversion efficiency (PCE) of the heterostructure thin-film solar cell reaches 21.4 %. The results of our research indicate that the controllable band alignment of CsSnBr 3 /MoX heterostructures has significant potential for future applications in optoelectronics.