Van der Waals epitaxy of type-II band alignment CsPbI3/TMDC heterostructure for optoelectronic applications

Van der Waals epitaxy allows heterostructure formation without considering the lattice match requirement, thus is a promising method to form 2D/2D and 2D/3D heterojunction. Considering the unique optical properties of CsPbI3 and transition metal dichalcogenides (TMDCs), their heterostructure presents potential applications in both photonics and optoelectronics fields. Here, we demonstrate selective growth of cubic phase CsPbI3 nanofilm with thickness as thin as 4.0 nm and zigzag/armchair oriented nanowires (NWs) on monolayer WSe2. Furthermore, we show growth of CsPbI3 on both transferred WSe2 on copper grid and WSe2–based optoelectrical devices, providing a platform for structure analysis and device performance modification. Transmission electron microscopy (TEM) results reveal the epitaxial nature of cubic CsPbI3 phase. The revealed growth fundamental of CsPbI3 is universal valid for other two-dimensional substrates, offering a great advantage to fabricate CsPbI3 based van der Waals heterostructures (vdWHs). X-ray photoelectron spectroscopy (XPS) and optical characterization confirm the type-II band alignment, resulting in a fast charge transfer process and the occurrence of a broad emission peak at lower energy. The formation of WSe2/CsPbI3 heterostructure largely enhances the photocurrent from 2.38 nA to 38.59 nA. These findings are vital for bottom-up epitaxy of inorganic semiconductor on atomic thin 2D substrates for optoelectronic applications.