Polymerized small-molecule acceptors based on vinylene as π-bridge for efficient all-polymer solar cells

Abstract

Two near-infrared (NIR) polymer acceptors (PAs, PYV, and PYV-Tz) based on fused-ring 2,1,3-benzothiadiazole (BT)- or benzotriazole (BTz)-based A′-DAD-A′ structure as electron-deficient-core and vinylene as the linking units, were designed and synthesized. The structure-property relationships of the all-polymer solar cells (all-PSCs) with a wide bandgap PBDB-T as donor were investigated systematically. Compared to the BT-based PA PYV, using BTz unit as the central core in PA PYV-Tz leads to the red-shifted absorption spectra and higher absorption coefficient in the PYV-Tz neat film. In addition, PYV-Tz also exhibits a higher lowest unoccupied molecular orbital (LUMO) energy level and better electron mobility. Consequently, the PBDB-T:PYV-Tz all-PSCs displayed a PCE of 13.02%, under the illumination of AM 1.5G, 100 mW cm-2, which is much higher than that of the PBDB-T:PYV device (11.51%). The measurements of relevant physical dynamics and blend morphologies further demonstrated the photovoltaic performance differences between PBDB-T:PYV and PBDB-T:PYV-Tz. This result indicates that PYV-Tz is a promising polymer acceptor material for the potential application of all-PSCs.