Reversed Y-shape di-anchoring sensitizers for dye sensitized solar cells based on benzimidazole core

Three new Y-shaped D-(pi-A)(2) di-anchoring organic dyes comprising an arylamine as the electron donor, 2-cyanoacrylic acid as electron acceptors and various 2,4,7-trisubstituted benzimidazole entity as theirlinkers/spacers, have been synthesized for dye-sensitized solar cells. The new dyes MD2 and MD3 show red-shifted absorption in solution spectra when compared with their congeners (8b and 9b) without electron-donating hexyloxy substituents. The N-alkyl at the benzimidazble, though helps with improved solubility, apparently results in serious twist between the benzimidazole core and the neighboring thienyl rings in the conjugated segment connected to the acceptor facing the N-alkyl or the phenyl ring connected to the arylamine donor. Photophysical and electrochemical measurements as well as theoretical computations were carried out on the new dyes. In addition to current voltage scan and incident photon to electron conversion efficiency (IPCE), electrochemical impedance spectroscopic (EIS) studies were also conducted. The dye MD3 exhibited the highest light-to-electric energy conversion efficiencies of 6.45% and 6.69%, respectively, for DSSCs without and with CDCA co-adsorbent. Better cell performance of MD3 than 9b can be attributed to better light harvesting and better dark current suppression of the former. (C) 2017 Elsevier Ltd. All rights reserved.