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Panchromatic Donor–Acceptor–Donor Conjugated Oligomers for Dye-Sensitized Solar Cell Applications

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journal contribution
posted on 11.06.2014, 00:00 by Romain Stalder, Dongping Xie, Ashraful Islam, Liyuan Han, John R. Reynolds, Kirk S. Schanze
We report on a sexithienyl and two donor–acceptor−donor oligothiophenes, employing benzothiadiazole and isoindigo as electron-acceptors, each functionalized with a phosphonic acid group for anchoring onto TiO2 substrates as light-harvesting molecules for dye sensitized solar cells (DSSCs). These dyes absorb light to wavelengths as long as 700 nm, as their optical HOMO/LUMO energy gaps are reduced from 2.40 to 1.77 eV with increasing acceptor strength. The oligomers were adsorbed onto mesoporous TiO2 films on fluorine doped tin oxide (FTO)/glass substrates and incorporated into DSSCs, which show AM1.5 power conversion efficiencies (PCEs) ranging between 2.6% and 6.4%. This work demonstrates that the donor–acceptor–donor (D-A-D) molecular structures coupled to phosphonic acid anchoring groups, which have not been used in DSSCs, can lead to high PCEs.