Investigation of the structure–performance correlation in Y-series electron acceptors with different phenyl alkyl inner side chains toward high-efficiency organic solar cells

and FF of OSCs show the same trend from D18:Y6-PhC4 and D18:Y6-PhC6 to D18:Y6-PhC8 pairs. Therefore, D18:Y6-PhC6 based devices achieve the highest power conversion efficiency (PCE) of 17.12%. Furthermore, D18:L8-BO:Y6-PhC6 based ternary OCSs are fabricated to afford an impressive PCE of 19.22%, benefiting from the superior properties of Y6-PhC6. This work manifests the importance of inner side chain engineering in regulating intrinsic properties and photovoltaic performance of Y-series NFAs.