Extension A unit in D-A polymer donor leads to higher JSC and FF for non-fullerene organic solar cells

Abstract

Two copolymer donors based on the thiophene-vinylene-thiophene (TVT) and thieno[3,2-b]thiophene-vinylene-thieno[3,2-b]thiophene (TTVTT) derivative, which were denoted as VT and VDT, respectively, were synthesized and applied to organic solar cells (OSCs). Detailed investigations revealed that the extension of conjugation can affect the optical and electronic properties, molecular aggregation, charge separation in the bulk-heterojunction films, and thus the overall photovoltaic performances. Without any additives or post-solvent/thermal annealing processes, the OSCs based on VDT: Y6 and VT: Y6 exhibited optimal power conversion efficiencies (PCEs) of 12.67% and 8.85%, respectively. These results indicate that extending the π-electron delocalization of the copolymer donors to broaden the absorption range and enhance intermolecular packing is an effective strategy to promote the device's performances.