Synthesis of dithieno[3,2-b:2′,3′-d]benzo[1,2-c][1,2,5]thiadiazole-cored polymerized small-molecule acceptors with ordered backbone stacking and their application in all-polymer solar cells

In recent years, polymerized small molecule acceptors (PSMAs) have emerged as a promising strategy that combines the strong absorption of small molecules with the film-forming ability and stability of polymers, thereby greatly boosting the performance of all-polymer solar cells (all-PSCs). We designed a non-fused acceptor, DTBT-IC, and its polymeric counterpart, PDTBT-Br-T, by selecting DTBT as the core, bithiophene as the π-bridge, and IC as the terminal group. PDTBT-Br-T was synthesized via Stille coupling and used with PM6 as the donor to fabricate organic solar cells. The PDTBT-Br-T-based device delivered superior performance, with a V_OC of 1.050 V, J_SC of 9.32 mA cm⁻², FF of 45.33%, and a PCE of 4.44%, outperforming the DTBT-IC-based counterpart. Morphological and structural analyses revealed that PDTBT-Br-T exhibits more ordered backbone stacking and defined phase separation, enhancing exciton dissociation and charge transport, and suppressing energy loss. The study highlights that polymerization of DTBT-IC enhances intermolecular packing and microstructure, offering critical design insights for efficient all-PSCs.