Covalent Triazine Framework Graphene-like Films Induce Growth of CsPbBr₃ Crystals for Efficient Inorganic Perovskite Solar Cells

Poor crystal quality is still the bottleneck for achieving high-performance photovoltaic devices. Here, we successfully fabricated exfoliated covalent triazine framework (ECTF) graphene-like films to induce the production of high-quality CsPbBr₃ films with monolayered large grains. Based on the coordination action between pyridinic N and Pb²⁺, the crystalline ECTF film can precisely induce the in situ reaction of PbBr₂ and CsBr to produce high-quality CsPbBr₃@ECTF-1 films via the self-assembling stacking effect derived from the π–π bond force. The obtained CsPbBr₃@ECTF-1 films have fewer grain boundaries, better charge transfer, and superior photoelectron and hole separation in comparison to the pristine CsPbBr₃ film. As a result, the champion efficiency of the CsPbBr₃@ECTF-1 solar cell (9.49%) improved by 15% over the pure CsPbBr₃ ones with significant increases in J_sc, V_oc, and FF. This encouraging result demonstrates that the ECTF graphene-like film template-induced strategy is an essential route to deposit monolayered large-grain perovskite films.