Fused octacyclic electron acceptor isomers for organic solar cells

We extend thieno[3,2-b]thiophene and naphthalene cores in our previously reported fused-ring electron acceptors (FREAs) F6IC and IHIC2 to benzo[b]benzo[4,5]thieno[2,3-d]thiophene and naphtho[1,2-b:5,6-b′]dithiophene, respectively, and synthesize two new isomeric FREAs BTIC and NTIC. Both BTIC and NTIC exhibit strong absorption from 500 to 800 nm with high extinction coefficients (2.4–2.6 × 105 M−1 cm−1) and electron mobilities of 1.8–3.4 × 10−4 cm2 V−1 s−1. Paired with the polymer donor PM6, the BTIC and NTIC-based organic solar cells (OSCs) show power conversion efficiencies (PCEs) of 11.5–12.2%, much higher than those of the control devices based on IHIC2 and F6IC (7.21–7.31%). The PM6/NTIC-based OSCs afford a higher PCE of 12.2% than PM6/BTIC-based OSCs (11.5%), due to the red-shifted absorption and up-shifted HOMO of NTIC.