Incorporation of plasmonic Au nanostars into photoanodes for high efficiency dye-sensitized solar cells

We have significantly improved the performance of dye-sensitized solar cells (DSSCs) by incorporating plasmonic Au nanostars into the TiO₂ photoanode. Gold nanostars were synthesized and used as localized surface plasmons (LSPs) to enhance the light absorption of DSSCs. The Au nanostars exhibit near infrared (NIR) light absorption at ∼785 nm. The N719 and N749 dye based DSSC devices were fabricated with and without the incorporation of Au nanostars. The power conversion efficiency (PCE) of DSSCs using Au nanostars was increased by ∼20% from 7.1% to 8.4% for N719 cells and by ∼30% from 3.9% to 5.0% for N749 devices. The incident photon-to-current conversion efficiency (IPCE) was improved and the spectral response was broadened over the wavelength range of 380-1000 nm. Electrochemical impedance spectroscopy (EIS) showed that by incorporating Au nanostars, the charge recombination resistance R_ct value decreased under both open-circuit and illumination conditions, which indicated high electron density generated in the device photoanode.