Synthesis of fluorinated phenylene-alkoxybenzothiadiazole polymer (PDTBTBz-2F anti ) by DHAP

Abstract

Conjugated polymers have garnered significant attention in the field of organic photovoltaics (OPVs) due to their lightweight, flexibility, and tunable properties. However, challenges related to scalability, environmental impact, and batch-to-batch reproducibility still hinder their commercial viability. In this work, we present a new synthesis route for the high-performance polymer PDTBTBz-2Fanti, known for achieving power conversion efficiencies (PCEs) of up to 9.8% in organic solar cells (OSCs) when paired with PC₇₁BM. Our approach replaces conventional Stille polymerization, which relies on toxic organotin compounds, with direct (hetero)arylation polymerization (DHAP), a greener alternative that reduces synthetic steps and hazardous by-products. Additionally, the alkoxybenzothiadiazole unit was partially sourced from biomass. To identify the route yielding a material most comparable to the reference polymer, two polymerization pathways employing different monomers were explored. Organic solar cells fabricated with the resulting materials confirmed that one pathway produced higher-quality polymers. Complementary density functional theory (DFT) calculations provided insight into potential structural defects, which were later supported by experimental findings. Finally, the optimized DHAP pathway was evaluated under continuous flow conditions, to further investigate this synthetic methodology.