Ethanol‐Assisted Green‐Solvent‐Based Strategy for Slot‐Die Coated Perovskite Solar Cells with over 70% Eco‐Friendly Solvent Content

Abstract Perovskite solar cells (PSCs) have recently achieved remarkable power conversion efficiencies, yet their commercial viability critically depends on the development of scalable, eco‐friendly fabrication processes. In particular, eliminating the use of toxic solvents such as N,N‐dimethylformamide (DMF) and 2‐methoxyethanol in slot‐die coating remains a major challenge. Here, a green solvent engineering strategy is presented that reduces hazardous solvent content by incorporating ethanol, a benign, low toxicity solvent, into the perovskite precursor solution. In the formulation, the fraction of hazardous solvents is reduced from 50% to 30% by volume. The introduction of ethanol improves substrate wetting and optimizes vapor pressure, both of which are key for achieving uniform film formation in scalable coating processes. Notably, increasing the ethanol content enhances the crystallinity and morphological uniformity of the perovskite films fabricated via slot‐die coating. As a result, a champion power conversion efficiency of 23.72% is achieved, and improved device stability is demonstrated under continuous operation, with performance maintained for over 750 hours under maximum power point tracking. This work highlights a viable pathway toward environmentally responsible and scalable PSC manufacturing.