19.1% efficiency all-polymer solar cells enabled by solvent and solid additives

Polymeric acceptors are prone to over-aggregate in photovoltaic thin films due to the entanglement of their long macromolecular chains, which hampers the exciton dissociation during the power conversion process. Although high boiling point solvent can retard the over-aggregation of polymeric acceptors, the structural order is often suppressed which will limit the charge transport in all-polymer solar cells (all-PSCs). In this work, the solvent additive 1-CN and solid additive INMB-F are combined to overcome the above issue, realizing enhanced structural order with refined phase separation in a cutting-edge PM6:PY-IT all-PSC, with a remarkable power conversion efficiency of 19.1%, which is one of the highest efficiency reported for binary PY-IT based all-PSCs. Molecular dynamics simulations and X-ray diffraction indicate that 1-CN can facilitate the disentanglement of PY-IT chains, while INMB-F can interact with these disentangled chains to promote ordered molecular stacking, thereby enhancing exciton dissociation and charge transport simultaneously.