Zn and Sr co-doped TiO2 mesoporous nanospheres as photoanodes in dye sensitized solar cell

Highlights: • Zn, Sr co-doped mesoporous TiO₂ showed best efficiency of 4.6% with short circuit photocurrent density of 8.63 mA/cm⁻². • EIS measurement showed that doping of zinc reduced the recombination and enhanced the electron transport. • STEM-mapping showed the Zn and Sr were homogenously distributed on the surface of TiO₂ nanosphere. -- Abstract: Mesoporous TiO₂ nanospheres that were co-doped with Zn and Sr were synthesized via a simple hydrothermal method. These materials were used as the photoanode in dye-sensitized solar cells (DSSCs). Field-emission electron microscopy showed that the nanospheres were monodisperse and interconnected, while transmission electron microscopy (TEM) showed that the nanospheres were composed of different nanostructures (nanotubes, diamond and sheet-like structures). Scanning TEM showed a homogeneous distribution of Sr, Ti, Zn and O throughout the nanospheres. When the Zn, Sr co-doped mesoporous TiO₂ nanospheres were incorporated into DSSCs, a device efficiency of 4.6%, a short circuit photocurrent density of 8.63 mA cm⁻² and an open circuit voltage 0.72 V were achieved. The efficiencies of these devices were higher than that of a comparison device (2.9%) that contained TiO₂ (P25).