Design and characterization of heteroleptic ruthenium complexes containing benzimidazole ligands for dye-sensitized solar cells: The effect of thiophene and alkyl substituents on photovoltaic performance

Wei Kai Huang, Hui Ping Wu, Pi Lun Lin, Wei-Guang Diau*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

We designed heteroleptic ruthenium complexes RD16-RD18 containing fluoro-substituted and thiophene-based benzimidazole ligands for dye-sensitized solar cells. Whereas the substitution of only fluorine in the RD12 device has an effect of enhancing the open-circuit voltage (VOC), additional substitution of thiophene in the RD16-RD18 sensitizers showed a slightly decreased VOC. Systematic enhanced short-circuit current density (JSC) and efficiency (η) of power conversion of the devices had the order RD18 > RD17 > RD16 > RD12 > N719, attributed to the increasing light-harvesting ability and the broadened spectral features with thiophene-based ligands. Measurements of charge extraction and intensity-modulated photovoltage spectra indicate that thiophene substitution shifts downward the TiO2 potential and accelerates charge recombination, but inclusion of a long hexyl chain on the thiophene moiety retards charge recombination to account for the variation of VOC in the series. For a duration test of device performance at ambient temperature, only ∼2% degradation of cell performance was found for the devices of RD18 and RD12 over 2000 h, but a 10% decrease in overall efficiency was observed in the N719 device.

Original languageEnglish
Pages (from-to)2175-2182
Number of pages8
JournalJournal of Physical Chemistry C
Volume117
Issue number5
DOIs
StatePublished - 7 Feb 2013

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