Star-shaped polymer acceptors reduce entanglement in all-polymer solar cells processed with non-halogenated solvents

All-polymer solar cells (all-PSCs) have seen significant advancements by the development of polymerized small molecular acceptors (PSMAs). However, the strong chain entanglement that occurs between polymer donors (PDs) and polymer acceptors (PAs) in halogenated solvents, such as chloroform, can limit the miscibility of the resulting polymer mixtures and hinder optimal blend morphologies. In this work, we designed two star-shaped PAs, PY-Ta and PYF-Ta, which reduce chain entanglement due to enough internal space in this dendritic star-shaped structure. In addition, the hot spin-coating strategy in the non-halogenated o-xylene (o-XY) can effectively alleviate chain entanglement in the PM6 donor. By combining the molecular design of PAs with a non-halogenated solvent hot spin-coating strategy, the PM6 can penetrate into the PAs material, enhancing their miscibility and promoting blend morphology. The star-shaped PAs exhibited better miscibility with PM6 compared to the linear PY-IT acceptor, achieving higher power conversion efficiencies (PCEs) of 16.92% and 16.60% for PM6:PY-Ta and PM6:PYF-Ta devices. Moreover, incorporating the high crystallinity and red-shifted PY-IT as a third component into the PM6:PY-Ta blend improved the absorption spectrum and morphology, leading to an outstanding PCE of 18.35%, setting a new benchmark for all-PSCs using non-halogenated fabrication.