Heteroleptic ruthenium(II) bipyridyl complex, cis-Ru(II)(4,4'-bis(4-tert-butylstyryl)-2,2'-bipyridyl) (4,4'-dicarboxy-2,2'-bipyridyl) (NCS 2 ) (H112) was synthesized and characterized by 1 H-NMR, MASS, Spectrofluorometer and UV-Vis spectroscopes. The photo-voltaic performance of the sensitizer was evaluated in Dye Sensitized Solar Cell (DSSC) under irradiation of AM 1·5 G solar light and the photovoltaic characteristics were compared with those of reference cells of HRS1 and N719 fabricated under comparable conditions. Compared to N719, H112 sensitizer showed enhanced molar extinction coefficient and relatively better monochromatic incident photon-to-current conversion efficiency (IPCE) across the spectral range of 400 to 800 nm with solar energy-to-electrical conversion efficiency (η) of 2·43% [open circuit photovoltage (V OC ) = 0·631 V, short-circuit photocurrent density (J SC ) = 8·96 mA/cm 2 , fill factor (ff) = 0·430], while η values of 2·51% (V OC = 0·651 V, J SC = 9·41mA/cm 2 , ff = 0·410) and 2·74% (V OC = 0·705 V, J SC = 8·62 mA/cm 2 , ff = 0·455) were obtained for HRS1 and N719 sensitized solar cells respectively. The introduction of 4,4'-bis(4-tert-butylstyryl) moieties on one of the bipyridine moieties of N719 complex shows higher light absorption abilities, IPCE and J SC .

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The new sensitizer MC119 has been synthesized and the solar cell constructed with 0.25 cm(2) active area photoelectrode in combination with an electrolyte composed of 0.6 M dimethylpropyl-imidazolium iodide (DMPII), 0.05 M I(2), 0.5 M TBP and 0.1 M LiI in acetonitrile achieved a solar to electric energy conversion efficiency (η) of 8.36% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell exhibited η-value of 7.2%.

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) 2 H101", where Ln = 4,4'-dicarboxylic acid-2,2'-bipyridine; was synthesized and characterized by 1 H-NMR, FT-IR and ESI-MASS spectroscopes. The H101 sensitized solar cell constructed with an active area of 0.54 cm 2 in combination with an ionic liquid electrolyte exhibited broader photocurrent action spectrum with solar-to-electric energy conversion efficiency (η) of 5.89 (J SC = 12.14 mA/cm 2 , V 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) 2 ', Z907 sensitized solar cell exhibited η-value of 5.17% (J SC = 11.93 mA/cm 2 , V 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 unoccupied frontier orbitals have π *-combinations with 4,4'-bis(3,5-di-tert-butylphenyl)-2,2'-bipyridine.

Four new small molecules CSDPP9–CSDPP12 were obtained with appended electron donating units in the molecular terminals of a DPP core. On solvent and thermal annealing, for the CSDPP11:PC71BM blend, the BHJ device displayed a PCE of 5.47%.