Atom-triggered epitaxial growth of Bi-based perovskite heterojunctions for promoting interfacial charge transfer

The construction of high-quality heterojunction with staggered band structure and close-contact interface, to satisfy both the thermodynamic and dynamic prerequisites of charge transfer, is the key to improve the charge separation of halide perovskites. The in situ growth of perovskite heterojunction via cosharing atoms provides an appealing solution to tackle this dilemma, but it remains a big challenge owing to the lack of appropriate precursors. Here, we design a novel visible-light responsive CoxBi2−xO2CO3 nanosheet, and use it as self-template to epitaxially grow Cs3Bi2Br9 nanosheet. It is revealed that close-contact 2D/2D heterointerfaces with strong chemical and electronic coupling are built via Bi atom bridge. Moreover, incorporating Co3+ into Bi2O2CO3 plays critical roles in heterojunction growth by regulating both the electronic structure and growth dynamics of Cs3Bi2Br9. Triggered by the effect of Co and the matched Bi lattice with Cs3Bi2Br9, the CoxBi2−xO2CO3/Cs3Bi2Br9 heterojunction can drive the fast Z-scheme transfer and separation of photoexcited charge carriers.