High Extinction Coefficient “Antenna” Dye in Solid-State Dye-Sensitized Solar Cells: A Photophysical and Electronic Study

We present a photophysical and device-based investigation of a new bipyridyl−NCS ruthenium complex sensitizer with an extended π system, in both sensitized TiO2 and incorporated into solid-state dye-sensitized solar cells. We compare this new sensitizer to an analog dye without the extended π system. We observe very similar excited-state absorption spectra and charge recombination kinetics for the two systems. However, the π-extended senstizer has a phenomenally enhanced molar extinction coefficient which translates into far greater light harvesting and current collection in solid-state dye-sensitized solar cells. We also infer from transient photovoltage measurements that positioning the pendent extended π system away from the TiO2 surface has induced a favorable dipole shift, generating enhanced open-circuit voltage. The resulting power conversion efficiency for the solar cell has been increased from 2.4% to 3.2% when comparing the new sensitizer to an analogy with no pendent group.