Biomimetic Mineralization Nucleation with Polymer Template Enabled High‐Performance Perovskite Solar Cells by Anti‐Solvent‐Free Technology

Abstract Nucleation regulation in the perovskite film‐forming process has been widely studied to optimize crystal quality and enable high‐efficiency perovskite solar cells (PVSCs) by an anti‐solvent‐free method. However, the vertical nucleation process is often difficult to control in anti‐solvent‐free preparation, due to the heterogeneous metal ion distribution and subsequent non‐uniform nucleation. Inspired by natural biomineralization mechanisms, this is pioneered that the introduction of a functional biopolymer carboxymethyl chitosan (CMC) at the buried interface of the perovskite layer, which would promote homogeneous vertical nucleation. Furthermore, CMC can improve perovskite film quality, passivate interfacial defects, and mitigate residual stresses. Finally, PVSCs with CMC prepared by anti‐solvent‐free method exhibit a remarkable PCE of 25.12%, ranking among the highest devices fabricated without anti‐solvent, while also exhibiting significantly improved stability. Encouragingly, the large‐area PVSCs (1 cm²) achieved an excellent PCE of 24%. This is believed that this work offers a robust strategy for optimizing anti‐solvent‐free fabrication processes for scalable and printable PVSCs.