Synthesis and characterization of new low band‐gap polymers containing electron‐accepting acenaphtho[1,2‐c]thiophene‐S,S‐dioxide groups

Two donor-acceptor conjugated polymers, PTSSO-TT and PTSSO-BDT, composed of acenaphtho[1,2-c] thiophene-S, S-dioxide (TSSO) as a new electron acceptor and thienothiophene (TT) or benzo[1,2-b: 4,5-b'] dithiophene (BDT) as electron donors, were synthesized with Stille cross-coupling reactions. The number-averaged molecular weights (M-n) of PTSSO-TT and PTSSO-BDT were found to be 15100 and 26000 Da, with dispersity of 1.8 and 2.4, respectively. The band-gap energies of PTSSO-TT and PTSSO-BDT are 1.56 and 1.59 eV, respectively. The HOMO levels of PTSSO-TT and PTSSO-BDT are -5.4 and -5.5 eV, respectively. These results indicate that the inclusion of TSSO accepting units into polymers is a very effective method for lowering their HOMO energy levels. The field-effect mobilities of PTSSO-TT and PTSSO-BDT were determined to be 1.5 x 10(-3) and 4.5 x 10(-4) cm(2) V-1 s(-1), respectively. A polymer solar cell device prepared with PTSSO-TT as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.79% with an open circuit voltage of 0.71 V under AM 1.5 G (100 mW cm(-2)) conditions. (C) 2015 Wiley Periodicals, Inc.