Influence of morphology on the plasmonic enhancement effect of Au@TiO2 core-shell nanoparticles in dye-sensitized solar cells

Plasmonic core-shell nanoparticles (PCSNPs) can function as nanoantennas and improve the efficiency of dye-sensitized solar cells (DSSCs). To achieve maximum enhancement, the morphology of PCSNPs needs to be optimized. Here we precisely control the morphology of Au@TiO₂ PCSNPs and systematically study its influence on the plasmonic enhancement effect. Enhancement mechanism was found to vary with the thickness of TiO₂ shell. PCSNPs with thinner shell mainly enhance the current, whereas particles with thicker shell also improve the voltage. While pronounced plasmonic enhancement was found in the near infrared regime, wavelength-independent enhancement in the visible range was observed and attributed to plasmonic heating effect. Emission lifetime measurement confirms that N719 molecules neighboring nanoparticles with TiO₂ shell exhibit longer lifetime than those in contact with metal cores. Overall, PCSNPs with 5-nm shell give highest efficiency enhancement of 23%. Our work provides a new synthesis route for well-controlled Au@TiO₂ core-shell nanoparticles and gains insight into the plasmonic enhancement in DSSCs.