Architecturing Lattice-Matched Bismuthene–SnO2 Heterojunction for Effective Perovskite Solar Cells

To explore the attractive structural and semiconductive properties of two-dimensional bismuthene, exquisite heterojunctions with less interfacial mismatch between bismuthene and SnO2 nanoparticle are coincidentally architected by a low-temperature procedure, based on a unique self-adaptive attribute of the two-dimensional structure of bismuthene, in combination with the lattice-matching attribute of adjacent lattice-spacing between bismuthene and SnO2. When applied in perovskite solar cells as an electron transport layer, the bismuthene–SnO2 composite layer turns smoother and more transparent and endows higher crystallinity to the upper perovskite layer. Depending on highly conductive bismuthene along with semiconductive bismuthene–SnO2 heterojunctions, the energy band of the integral composite layer is upshifted and the interfacial resistance between the composite layer and the perovskite layer is reduced, effectively accelerating the electron extraction without declining the hole-blocking, in comparison with the pure SnO2 layer. A higher statistical average power conversion efficiency of 18.75% is achieved, compared to the counterpart of 17.35%, and it also maintains a high stability of almost 80% of its initial efficiency even in an ∼5% relative humidity environment for more than 800 h, in contrast to its counterpart, which maintains just 50% efficiency retention.