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. The biaxial strains originating from the lattice mismatch endow the monolayer SnS an indirect‐to‐direct bandgap transition. Moreover, the interface effect in turn reduces the band offset of the CsPbI3/SnS heterostructure and enhances its optical absorption ability. Therefore, forming heterostructure can promote the properties of CsPbI3‐based devices.