SiO2/TiO2 Hollow Nanoparticles Decorated with Ag Nanoparticles: Enhanced Visible Light Absorption and Improved Light Scattering in Dye-Sensitized Solar Cells

Hollow SiO2/TiO2 nanoparticles decorated with Ag nanoparticles (NPs) of controlled size (Ag@HNPs) were fabricated in order to enhance visible-light absorption and improve light scattering in dye-sensitized solar cells (DSSCs). They exhibited localized surface plasmon resonance (LSPR) and the LSPR effects were significantly influenced by the size of the Ag NPs. The absorption peak of the LSPR band dramatically increased with increasing Ag NP size. The LSPR of the large Ag NPs mainly increased the light absorption at short wavelengths, whereas the scattering from the SiO2/TiO2 HNPs improved the light absorption at long wavelengths. This enabled the working electrode to use the full solar spectrum. Furthermore, the SiO2 layer thickness was adjusted to maximize the LSPR from the Ag NPs and avoid corrosion of the Ag NPs by the electrolyte. Importantly, the power conversion efficiency (PCE) increased from 7.1% with purely TiO2-based DSSCs to 8.1% with HNP-based DSSCs, which is an approximately 12% enhancement and can be attributed to greater light scattering. Furthermore, the PCEs of Ag@HNP-based DSSCs were 11% higher (8.1 vs. 9.0%) than the bare-HNP-based DSSCs, which can be attributed to LSPR. Together, the PCE of Ag@HNP-based DSSCs improved by a total of 27%, from 7.1 to 9.0%, due to these two effects. This comparative research will offer guidance in the design of multifunctional nanomaterials and the optimization of solar-cell performance.