High-Efficiency All-Polymer Solar Cells with Poly-Small-Molecule Acceptors Having π-Extended Units with Broad Near-IR Absorption

We report two new poly-small-molecule acceptors, PYN-BDT and PYN-BDTF, which serve, by virtue of their p-extended naphthalene rings, as broad optical cross-section macromolecular absorbers (extending to similar to 900 nm; Delta E-opticalgap = 1.38 eV) in all-polymer solar cells (APSCs). APSCs fabricated by blending PYN-BDT or PYN-BDTF with PM6 exhibit power conversion efficiencies (PCEs) of 7.24 and 9.08%, respectively, while blends with PBDB-T exhibits far higher PCEs of 12.06 and 13.22%, respectively; the latter cell achieves J(sc) = 22.28 mA cm(-2), among the highest known for an APSC. The results of blend morphology, GIWAXS, charge transport, exciton and carrier dynamics, PL quenching efficiency, and impedance-based analysis indicate that the PBDB-TT:PYN-BDTF blends and their APSCs outperform the corresponding PM6:PYN-BDTF devices due to significantly suppressed bimolecular recombination. These results demonstrate that pi-conjugative extension of individual polymer acceptor blocks represents an efficient strategy to broaden APSC optical cross sections, decrease bimolecular recombination, and achieve high-performance cells with enhanced J(sc) metrics.