Pb‐Rich Buried Interface Promoting Upward Unidirectional Crystallization for Efficient and Stable Carbon‐Based Perovskite Solar Cells and Mini‐Modules

ABSTRACT Improving the crystalline quality of perovskite films is the most effective approach for constructing high‐performance carbon‐based perovskite solar cells (C‐PSCs). In particular, highly (100)‐oriented monolayer perovskite films can effectively suppress defect‐induced recombination while enhancing charge transport, thereby reducing non‐radiative recombination losses in C‐PSCs. In this work, we propose a scalable strategy for constructing a Pb‐rich modified buried interface with abundant Pb sites, which promotes perovskite nucleation and induces an upward unidirectional crystallization process, resulting in large‐grained, (100)‐oriented perovskite films. Moreover, the Pb‐rich interface layer of Pb 10 (PO 4 ) 6 O exhibits better lattice matching with perovskite, significantly alleviating interfacial lattice strain at the buried interface. As a result, the fabricated C‐PSCs achieved a champion efficiency of 21.56%, as well as an efficiency of 18.12% for the carbon‐based mini‐module (10.08 cm 2 ), which is among the best reported efficiencies for hole transport layer‐free planar C‐PSCs. In addition, the maximum power point tracking of unencapsulated devices offered an outstanding T 90 lifetime exceeding 1000 h under the ISOS‐L‐1I standard protocol. These results confirm that the above strategy possesses excellent scalability and strong potential for large‐area perovskite photovoltaics.