Asymmetric Strain-Introduced Interface Effect on the Electronic and Optical Properties of the CsPbI3/SnS van der Waals Heterostructure

Different 2D materials can be stacked by the weak van der Waals (vdW) force, forming the vdW heterostructures and devices, which opens a new field of engineering regulation of electronic and optical properties at the atomic level. The asymmetric strain-introduced interface effect is studied on the electronic and optical properties of CsPbI3/SnS vdW heterostructure by employing first-principles calculations. The biaxial strains deriving from the interface mismatch reduce the work function of the monolayer SnS to a low-energy level, and lead to monolayer SnS an indirect-to-direct bandgap transition. The different charge transfer behaviors in the PbI2- (CsI-) surface indicate that monolayer SnS can act as the promising hole- (electron-) transport material of perovskite solar cells (PSCs). Moreover, the interface effect causes the absorption spectrum of the CsPbI3/SnS heterostructure an obvious redshift and enhances its absorption ability, which is more suitable for photovoltaic devices. This work suggests that the strain-introduced interface effect plays a significant role in the interface engineering of the vdW heterostructure between perovskite and 2D materials, which provides a new way to fabricate the high performance perovskite/2D materials heterostructure-based solar cells and optoelectronic devices.