Hot‐Casting Boosts Efficiency of Halogen‐Free Solvent Processed Non‐Fullerene Organic Solar Cells

Abstract

AbstractDespite the substantial climb of the power conversion efficiency (PCE) of organic solar cells (OSCs), the majority of processing solvent remains halogenated and stand as a critical issue for commercialization. Herein, a halogen‐free solvent system consisting of toluene (Tol) and 1‐phenylnaphthalene (PN) is used to replace the traditional halogenated chloroform (CF) and1‐chloronaphthalene (CN) for the processing of the PM6:M36 OSC, reducing the maximum PCE from 15.0% to 13.3%. Hot‐casting is demonstrated to boost the maximum PCE of halogen‐free solvents processed OSCs back to 15.2%. The preheated substrate fastens the evaporation of Tol and enables similar film‐forming kinetics to CF, resulting in the inhibition of immoderate molecular aggregation and excessive phase separation. Ternary OSCs, with either another donor or acceptor as the third component, can further improve device PCE to 15.8%, confirming the versatile photovoltaic systems that this hot‐casting method can be applied to. Encouragingly, the hot‐casting processed binary and ternary OSCs also exhibit retained storage stability. Therefore, hot‐casting is demonstrated as a superior strategy to fabricate OSCs without efficiency and stability loss using halogen‐free solvents.