Comparative hydrothermal synthesis of CeO₂crystals for use in light-scattering layers of dye-sensitized solar cells

Submicrometer-sized CeO₂crystals were synthesized by a hydrothermal reaction method, aiming at their use as light-scattering layers in dye-sensitized solar cells (DSSCs). The morphology of the crystals was varied among a round-cornered cubic, a distinct cubic, or an octahedral shape by changing the synthetic conditions. The film formability and the light-scattering ability of the CeO₂crystals, which were coated on glass substrates by a squeegee method, were found to be dependent on their morphology according to the microstructural observation and the diffuse reflectance measurement. The effects of the CeO₂light-scattering layer were then examined for DSSCs using nanoparticulate ZnO electrodes with different thicknesses and sensitizer dyes, namely N-719 and N-749, with different absorption spectra. A short-circuit photocurrent density could be enhanced, for example, from 11.20 to 14.15 mA cm⁻², by stacking the CeO₂layer on the ZnO electrode. The effectiveness of the light-scattering layer in the CeO₂/ZnO electrodes was discussed based on the CeO₂crystal morphology and the CeO₂film microstructure after the systematic investigation.