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- Title
Ruthenium(II)- bipyridyl with extended π-system: Improved thermo-stable sensitizer for efficient and long-term durable dye sensitized solar cells.
- Authors
CHANDRASEKHARAM, M; RAJKUMAR, G; SRINIVASA RAO, CH; SURESH, T; REDDY, P; SOUJANYA, Y
- Abstract
A new extended thermo-stable high molar extinction coefficient bipyridyl ruthenium(II) complex ' cis-Ru(4,4'- bis(3,5-di- tert-butylphenyl)-2,2'-bipyridine)( Ln)(NCS) H101', where Ln = 4,4'-dicarboxylic acid-2,2'-bipyridine; was synthesized and characterized by H-NMR, FT-IR and ESI-MASS spectroscopes. The H101 sensitized solar cell constructed with an active area of 0.54 cm in combination with an ionic liquid electrolyte exhibited broader photocurrent action spectrum with solar-to-electric energy conversion efficiency ( η) of 5.89 ( $\textbf{\textit{J}}_{\rm SC} =$ 12.14 mA/cm, $\textbf{\textit{V}}_{\rm OC} =$ 690 V, fill factor = 0.699) under Air Mass (AM) 1.5 sunlight, while the reference ' cis-Ru(4,4'-dinonyl-2,2'-bipyridine)( Ln)(NCS)', Z907 sensitized solar cell exhibited η-value of 5.17% ( $\textbf{\textit{J}}_{\rm SC} =$ 11.93 mA/cm, $\textbf{\textit{V}}_{\rm OC} =$ 650 V, fill factor = 0.666). TGA analysis of H101 showed extended thermal-stability and under continuous light exposure and aging at 55°C, the DSSC retained 85% of its initial η-value, while under comparable conditions Z907 sensitized solar cell retained 88%. As compared to 4,4'-dinonyl-2,2'-bipyridine in Z907, the new ancillary bipyridyl ligand '4,4'- bis(3,5-di- tert-butylphenyl)-2,2'-bipyridine' in H101 shifts the absorption bands remarkably towards blue. The Density Functional Theory (DFT) and Time-Dependent DFT excited state calculations of the new sensitizer show that the first three HOMOs have t2g character with sizeable mixing from the NCS ligands with π-bonding orbitals of 4,4'- bis(3,5-di- tert-butylphenyl)-2,2'-bipyridine. The LUMO is a π*-orbital localized on the 4,4-dicarboxylic acid-2,2'-bipyridine and higher un-occupied frontier orbitals have π*-combinations with 4,4'- bis(3,5-di- tert-butylphenyl)-2,2'-bipyridine. [Figure not available: see fulltext.]
- Subjects
RUTHENIUM; BIPYRIDINE; PHOTOSENSITIZERS; SOLAR cells; ELECTROLYTES
- Publication
Journal of Chemical Sciences, 2011, Vol 123, Issue 5, p555
- ISSN
0974-3626
- Publication type
Article
- DOI
10.1007/s12039-011-0121-4