Polypyridyl Ru(II)-sensitizers with extended pi-system enhances the performance of dye sensitized solar cells

New polypyridyl ruthenium(II) complexes "cis-Ru(4,4'-dimesity1-2,2'-bipyridine) (Ln) (NCS)(2) H102" and "cis-Ru(4,4'-bis(2,3,6-tri-isopropylphenyl)-2,2'-bipyridine) (Ln) (NCS)(2) H105", where Ln = 4,4'-dicarboxylic acid-2,2'-bipyridine; were synthesized and successfully applied to sensitization of nano-crystalline TiO2 based solar cells (DSSCs). The DSSCs of H102 and H105 fabricated from 0.16 cm(2) TiO2 electrodes exhibited broader comparable photocurrent action spectra with almost identical solar-to-electrical energy conversion efficiency (II) as compared to N719 sensitizer. The incident photon-to-current conversion efficiency (IPCE) values of 98% and 95% were obtained for H102 and H105 sensitizers respectively. Under 1 sun condition, eta-values of 8.39% (short-circuit photocurrent (J(SC))= 16.4 mA/cm(2), open-circuit photo voltage (V-OC) = 692 mV, fill factor = 0.734), 8.76% (J(SC) = 16.3 mA/cm(2), V-OC = 735 mV, fill factor = 0.734) and 9.12% (J(SC) = 16.1 mA/cm(2), V-OC = 745 mV, fill factor = 0.753) were obtained for H102, H105 and N719 sensitizers respectively. (C) 2011 Elsevier B.V. All rights reserved.