Sea urchin TiO₂–nanoparticle hybrid composite photoelectrodes for CdS/CdSe/ZnS quantum-dot-sensitized solar cells

The sea urchin TiO₂ (SU TiO₂) particles composed of radially aligned rutile TiO₂ nanowires are successfully synthesized through the simple solvothermal process. SU TiO₂ was incorporated into the TiO₂ nanoparticle (NP) network to construct the SU–NP composite film, and applied to the CdS/CdSe/ZnS quantum-dot-sensitized solar cells (QDSSCs). A conversion efficiency of 4.2% was achieved with a short-circuit photocurrent density of 18.2 mA cm⁻² and an open-circuit voltage of 531 mV, which corresponds to ∼20% improvement as compared with the values obtained from the reference cell made of the NP film. We attribute this extraordinary result to the light scattering effect and efficient charge collection.