DMF and Antisolvent Free Fabrication of {CH(NH2)2}1-xCsxPbI3 Perovskite Solar Cells via Volatility-Controlled Cosolvent

Perovskite solar cells (PSCs) have garnered considerable attention for their ability to deliver high-power conversion efficiencies through economical, solution-processed fabrication. However, reliance on toxic solvents such as N,N-dimethylformamide (DMF) and the antisolvent-dripping method poses challenges for large-scale manufacturing. This study presents an antisolvent-free, one-step spin-coating method for fabricating {CH(NH 2 ) 2 } 1-x Cs x PbI 3 (FA 1-x Cs x PbI 3 ) perovskite films using a volatility-controlled cosolvent. Using 2-methoxyethanol (2-ME) as a highly volatile primary solvent to drive rapid supersaturation, while 1-cyclohexyl-2-pyrrolidone (CHP) acts as a high-boiling-point cosolvent to moderate crystallization kinetics through intermediate stabilization. Crucially, CsCl is introduced as a strategic additive to overcome the inherent low solubility of conventional cesium precursors in 2-ME. CsCl appears to play dual roles: enabling effective Cs + incorporation to stabilize the α-phase perovskite and likely assisting crystallization by facilitating the formation of transient chloride-mediated intermediates. Optimizing the formulation with 3.5 vol% CHP and 7.5 mol% CsCl led to significant improvements in film uniformity, crystallinity, and optical properties. Consequently, n-i-p planar heterojunction solar cells fabricated using a 0.45 M precursor solution achieved a high-power conversion efficiency of 21.1% with short-circuit current density (25.8 mA/cm 2 ), open-circuit voltage (1.06 V), and fill factor (77.5%), and a stabilized output of 20.8%, confirming the potential of this DMF- and antisolvent-free process for scalable PSC production, while emphasizing that the present approach is based on volatility control rather than complete solvent detoxification. • Developed a DMF- and antisolvent-free one-step perovskite fabrication method • Utilized 2-methoxyethanol as the primary solvent with a CHP cosolvent • Improved film uniformity and crystallinity via CsCl additive incorporation • Achieved 21.1% power conversion efficiency in n-i-p planar solar cells • Promotes scalable perovskite solar cell production