Non-Fused Polymerized Small Molecular Acceptors for Efficient All-Polymer Solar Cells

Abstract

The development of polymer acceptors is critical to promote the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs). Herein, two novel polymer acceptors (PBTz-TT and PFBTz-TT) derived from non-fused small molecules, which possess synthetic simplicity, narrow optical bandgap, and high absorption coefficients, are reported for the first time. The all-PSCs are fabricated by a layer-by-layer deposition technique with PBDB-T as donor, and the device performance is improved by the synergistic effect of solvent additive and thermal annealing. As a result, the all-PSCs offer PCEs of 10.14% and 6.85% for PFBTz-TT and PBTz-TT, respectively. Further morphological and electrical characterizations unveil that the higher device performance of PFBTz-TT originates from more efficient exciton separation and charge transport as a result of more ordered polymer packing in solid state. Herein, it is demonstrated that polymerizing non-fused small molecular acceptors is an effective strategy to develop polymer acceptors for high-performance all-PSCs.