Balance Processing and Molecular Packing via Structural Disordering in a Random Terpolymer for Over 19% Efficiency Non‐Halogenated Solvent Organic Solar Cells

Abstract Achieving commercial viability for organic solar cells (OSCs) requires non‐toxic, non‐halogenated solvent processing. However, poor solubility and suboptimal morphology of commonly used active layer materials have been limiting their non‐halogenated solvent applications for high‐performance OSCs. This study introduces a novel random terpolymer, PM7‐TTz50, designed to overcome these challenges. By incorporating 50 mol% of a co‐planar thiophene‐thiazolothiazole (TTz) unit into the PM7 backbones, the resulting terpolymer achieves enhanced solubility in eco‐friendly solvents. Furthermore, PM7‐TTz50's strong aggregation tendency, coupled with high‐boiling‐point solvent processing—which prolongs aggregate/crystal growth—enhances molecular stacking and ordering. This approach supports efficient charge transport and minimizes non‐radiative recombination, yielding power conversion efficiencies (PCEs) exceeding 19% and over 16% w/o solvent additives. Additionally, PM7‐TTz50 demonstrates broad compatibility with various non‐fullerene acceptors (NFAs), leading to enhanced material uniformity and reproducibility in device fabrication.