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 x 10(5) M-1 cm(-1)) and electron mobilities of 1.8-3.4 x 10(-4) cm(2) 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.