Improvement of light-harvesting efficiency in dye-sensitized solar cells using silica beads embedded in a TiO2 nanoporous structure

The effect of various materials of the spherical scattering centre in a TiO2 nanoporous structure in dye-sensitized solar cells (DSSCs) was investigated by both theoretical simulation and experiment. Three materials, titania, electrolyte and silica, were investigated using the Mie Theory, in which the concepts of volume total cross section and solar spectrum were accommodated for better accuracy. Of those materials, silica was chosen in this study due to its perfectly transparent nature, easy size controllability and perfectly spherical shape, which make silica most suitable for understanding the scattering effect with a simple optical approach. The validity was proved by experiment with various sizes of silica beads (0.3, 0.6, 0.9, 1.2, 1.5 µm) embedded in DSSCs; experiments revealed the same trend as did the simulation. The overall efficiency of the DSSCs was increased by 20.4% using 300 nm diameter silica beads. The efficiency versus bead size had a peak with beads of 300 nm diameter and decreased as the bead size increased. This study showed that silica could be a good candidate for scattering particles in DSSCs. Furthermore, this study could be considered a valuable reference for further investigations of scattering phenomena by small spherical particles or arbitrary shape of particles in DSSCs.