A new type of carbene-based ruthenium sensitizer, CB104, with a highly conjugated ancillary ligand, diphenylvinylthiophene-substituted benzimidazolepyridine, was designed and developed for dye-sensitized solar cell applications. The influence of the thiophene antenna on the performance of the cell anchored with CB104 was investigated. Compared with the dye CBTR, the conjugated thiophene in the ancillary ligand of CB104 enhanced the molar extinction coefficient of the intraligand π-π* transition and the intensity of the lower energy metal-to-ligand charge-transfer band. However, the incident photon-to-current conversion efficiency spectrum of the cell anchored with CB104 (0.15 mM) showed a maximum of 63 % at 420 nm. The cell sensitized with the dye CB104 attained a power conversion efficiency of 7.30 %, which was lower than that of the cell with nonconjugated sensitizer CBTR (8.92 %) under the same fabrication conditions. The variation in the performance of these two dyes demonstrated that elongating the conjugated light-harvesting antenna resulted in the reduction of short-circuit photocurrent density, which might have been due to the aggregation of dye molecules. In the presence of a coabsorbate, chenodeoxycholic acid, the CB104-sensitized cell exhibited an enhanced photocurrent density and achieved a photovoltaic efficiency of 8.36 %.

Two novel oxindole sensitizers have been synthesized for dye-sensitized solar cell applications. These new dyes can provide an additional pathway to inject electrons into the photoanode through the partial chelation of their amide carbonyl groups to the TiO2 surface. Incorporation of an electron deficient pyridine in the acceptor of the TI125 dye was found to enhance the photovoltage and conversion efficiency of the cell.

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New D-π-A configured organic sensitizers featuring halogen-substituted oxindole-bridged acceptor units have been synthesized for dye-sensitized solar cells applications. Among fluorine, bromine, and iodine substitution, the cell based on bromine incorporated dye exhibited the highest efficiency. The oxindoles in these sensitizers were found to assist the electron injection through the chelation of their amide carbonyl groups to the TiO2 surface. This study provides an alternate approach for future rational dye design to gain excellent DSSC performance.