Greener Colloidal Ink Engineering and Local Solidification Control for High‐Performance Slot‐Die Coated Perovskite Solar Modules

ABSTRACT Perovskite solar cells (PSCs) have emerged as leading candidates for next‐generation photovoltaics; however, translating laboratory‐scale efficiencies to industrial production remains limited by key challenges such as achieving high‐quality film and addressing solvent toxicity. To overcome these limitations, we formulate colloidal ink by incorporating iodobenzene (Iodo) as an environmentally sustainable additive into a DMSO‐based system, enabling scalable film fabrication via slot‐die coating. It is found that Iodo‐based additives enhance wettability, facilitate the formation of larger colloidal particles, and enable controlled solidification through solvent evaporation kinetics. Specifically, the inclusion of Iodo modulates colloidal size and evaporation behavior, which in turn reduces the effective nucleation barrier and promotes directional grain growth. This leads to the formation of dense, uniform films with improved crystallinity and minimal defects. Devices fabricated using Iodo‐based ink achieved an efficiency of up to 22.3% (the highest reported efficiency in a highly toxic DMF‐free system), encapsulated devices retaining 85% of their initial value after 1200 h of maximum power point tracking (MPPT) and 77% after 8400 h (unencapsulated devices stored in the dark), demonstrating excellent operational and long‐term stability. Furthermore, the DMF‐free, DMSO‐based ink shows excellent scalability, achieving efficiencies of 21% and 19.5% for 2.7 and 31.50 cm ² modules, respectively.