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Thiocyanate‐Free Ru(II) Sensitizers with a 4,4′‐Dicarboxyvinyl‐2,2′‐bipyridine Anchor for Dye‐Sensitized Solar Cells
Author(s) -
Wu KuanLin,
Ku WanPing,
Wang ShengWei,
Yella Aswani,
Chi Yun,
Liu ShihHung,
Chou PiTai,
Nazeeruddin Mohammad K.,
Grätzel Michael
Publication year - 2013
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201201876
Subject(s) - dye sensitized solar cell , thiocyanate , materials science , energy conversion efficiency , open circuit voltage , bipyridine , photochemistry , chromophore , electrolyte , inorganic chemistry , crystallography , chemistry , electrode , optoelectronics , voltage , crystal structure , physics , quantum mechanics
Abstract A new class of thiocyanate‐free Ru(II) sensitizers with 4,4′‐dicarboxyvinyl‐2,2′‐bipyridine anchor and two trans ‐oriented pyrid‐2‐yl pyrazolate (or triazolate) functional chromophores is synthesized, characterized, and evaluated in dye‐sensitized solar cells (DSCs). Despite their enhanced red response and absorptivity when compared to the parent sensitizer TFRS‐2 that possesses standard 4,4′‐dicarboxyl‐2,2′‐bipyridine anchor and shows the best conversion efficiency of η = 9.82%, the newly synthesized carboxyvinyl‐pyrazolate sensitizers, TFRS‐11 – TFRS‐13 , exhibit inferior performance characteristics in terms of short‐circuit current density ( J SC ), open‐circuit voltage ( V OC ), and power conversion efficiency ( η ), the latter being recorded to be in the range 5.60–7.62%. The reduction in device efficiencies is attributed to a combination of poor packing of these sensitizers on the TiO 2 surface and less positive ground‐state oxidation potentials, which, respectively, increase charge recombination with I 3 − in electrolytes and impede the regeneration of sensitizers by I − anions. The latter obstacle can be circumvented in part by the replacement of the pyrazolates with triazolates, forming the TFRS‐14 sensitizer, which exhibits an improved J SC , V OC , and η of 16.4 mAcm −2 , 0.77 V, and 9.02%, respectively.