Enhanced photovoltaic performance of cross-linked ruthenium dye with functional cross-linkers for dye-sensitized solar cell

Photovoltaic performance of cross-linkable Ru(2,2-bipyridine-4,4-bicarboxylic acid)(4,4-bis((4-vinyl benzyloxy)methyl)-2,2-bipyridine)(NCS)(2) (denoted as RuS dye) adsorbing on TiO2 mesoporous film was enhanced by polymerizing with either ionic liquid monomer, 1-(2-acryloyloxy-ethyl)-3-methyl-imidazol-1-ium iodide (AMImI), to form RuS-cross-AMImI or di-functional acrylic monomer with ether linkage, triethyleneglycodimethacrylate (TGDMA), to form RuS-cross-TGDMA. Their cross-linking properties were investigated by UV-vis spectroscopy by rinsing with 0.1N NaOH aqueous solution. The power conversion efficiencies (PCEs) of dye-sensitized solar cells (DSSCs) with RuS-cross-AMImI and RuS-cross-TGDMA both reached over 8% under standard global air mass 1.5 full sunlight. The increased PCE for DSSCs with RuS-cross-AMImI comparing with cross-linked RuS was attributed to the I- counterion of AMImI increasing the charge regeneration rate of RuS dye, whereas that with RuS-cross-TGDMA was attributed to the Li+ coordination property of TGDMA. The photovoltaic performance of RuS-cross-TGDMA was also slightly better than that of RuS-cross-AMImI because of higher open-circuit photovoltage (V-oc) and short-circuit photocurrent (J(sc)). Its higher V-oc was supported by the Bode plot of impedance under illumination and Nyquist plots at dark, whereas higher J(sc) was supported by the incident monochromatic photon-to-current conversion efficiency spectra and charge extraction experiments. Copyright (c) 2013 John Wiley & Sons, Ltd.