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.