Two-dimensional SnS2 nanosheets as electron transport and interfacial layers enable efficient perovskite solar cells

Abstract

Despite great progress achieved for metal oxide electron transport layers (ETLs), finding alternative inorganic ETLs is necessary and meaningful to further boost the performance and stability of perovskite solar cells (PSCs), and also to expand the inorganic ETL family. Herein, 2D SnS₂ nanosheets prepared by a simple hydrothermal route are applied as low-temperature processed ETLs of PSCs. These SnS₂ ETLs show a compact and uniform surface, a high transparency, and a fast charge carrier mobility. PSCs based on sole SnS₂ ETLs show a high energy conversion efficiency of 18.5%, ranking top among the metal sulfide ETLs. Furthermore, the 2D SnS₂ nanosheets are used as an effective interfacial modifier for the traditional SnO₂ ETL, which forms an energy level gradient between SnO₂ and the perovskite layer. The SnS₂ interlayer improves the perovskite crystallization and passivates defects at the interface due to the optimized coupling, enabling a PCE of 21.5% for the SnO₂–SnS₂ bi-layer PSCs along with enhanced stability.