Coffee‐Ring‐Engineered Interfacial Layer Enables Fluid‐Locking for Scalable Perovskite Photovoltaics

ABSTRACT Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology, offering outstanding power conversion efficiency and significant potential for large‐scale deployment. However, during printed fabrication, the intrinsic coffee‐ring effect induces heterogeneous deposition of colloidal particles, leading to non‐uniform crystallization that critically limits the performance of large‐area devices. This issue not only complicates the crystallization dynamics of perovskite films but also impedes the development of a universal fluidic control strategy applicable across device scales. In this work, we harnessed the mechanisms of coffee‐ring formation and employed rapid drying combined with droplet fragmentation to construct a size‐tunable flow‐locking network at the buried interface. This network effectively confines the disordered migration of perovskite colloidal particles throughout the flowing and drying stages, suppressing the formation of macroscopic coffee rings and mitigating their detrimental impact on device crystallization and performance. As a result, the optimized PSCs deliver a high power conversion efficiency (PCE) of 26.61%, while a large‐area module (100 cm 2 ) maintains an impressive PCE of 21.39%, demonstrating excellent scalability and device uniformity.