Sustainable ternary solvent strategy for high-efficiency slot-die coated perovskite solar cells

Slot-die coating is a promising, scalable deposition technology to progress the commercialization of perovskite solar cells (PSCs), where solvent engineering is critical for producing sustainable high-performance devices. This is because the complex interaction between solvent properties and coating parameters has a significant impact on the quality of the perovskite film, which directly affects device performance. To address these challenges, in this work, we designed and demonstrated a more sustainable ternary solvent strategy combining dimethyl sulfoxide (DMSO), acetonitrile (ACN), and 1,3-dimethyl-2-imidazolidinone (DMI). Rheological and morphological studies confirmed that ACN reduces ink viscosity and surface tension while accelerating initial nucleation through its high evaporation rate, facilitating uniform wet-film formation during slot-die coating. Meanwhile, DMI modulates crystallization kinetics by suppressing secondary nucleation through its low vapor pressure and coordination bonding with organic cations, precisely controlling crystal growth. This synergistic effect results in perovskite films with superior morphological characteristics, including larger grain sizes, enhanced thickness, and significantly reduced defect density. Ultimately, the optimized PSCs exhibited a remarkable power conversion efficiency of 20.62 %, with excellent light, thermal, and long-term stability. This work provides valuable insights into solvent engineering strategies for scalable, high-performance PSC fabrication and establishes a new milestone for sustainable slot-die coated devices.