In situ ligand-free growth of TiO2-escapsulated Au nanocomposites on photoanode for efficient dye sensitized solar cells

As a kind of promising plasmonic materials, Au nanoparticles, especially Au-insulator core-shell nanostructures, offer great potential in the fields of catalysis, diagnosis, and energy conversion, however, it is still a challenge to fabricate protective-layer Au nanoparticles with desired performance using a facile strategy. In this work, we report a new synergistic method that combines in-situ ligand-free plasmonic treatment with TiCl4 treatment, resulting in the direct growth of quantum-size Au nanoparticles with thin TiO2 coating layer on photoanode. As a result, an excellent power conversion efficiency of 12.70% for the as-treated photoanode has been achieved with an open-circuit voltage of 816 mV and a short-circuit current density of 21.95 mA/cm2. This is one of the highest efficiencies reported to date for plasmonic dye sensitized solar cells (DSSCs). The obtained photovoltaic performance can be attributed to the improved light harvesting and charge collection efficiency, which is resulted from the plasmonic effect and Fermi level shift by the introduction of Au nanoparticles. Our work provides a simple and effective strategy for efficient DSSCs, yet it may also benefit to other solar conversion and photo-electro-catalysis devices.