Spherical anatase TiO2 covered with nanospindles as dual functional scatters for dye-sensitized solar cells

• Spherical anatase TiO2 covered with nanospindles (SNS) were employed in DSSCs.
• SNS possess the dual functions of light scattering and high dye loading.
• SNS were fabricated through a facile hydrothermal treatment of the precursors.
• Precursors were synthesized by controlled hydrolysis of TBT after being diluted.
• The cells based on SNS-18/P25 photoanode exhibited advanced performance.

Spherical anatase TiO2 covered with nanospindles (SNS) were fabricated through a facile hydrothermal treatment of precursors in the presence of ammonia. The precursors were synthesized by controlling hydrolysis rate of TBT (tetrabutyl titanate) in ethanol. Organic structure directing agents and toxic reagents were avoided in the two–step process. By scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), it is confirmed that the morphology and structure of the products can be controlled by adjusting hydrothermal treatment conditions. Time dependent trails revealed the growth mechanism of SNS, which indicating that ammonia can not only retard the dissolution of precursors but also make TiO2 grow selectively along the <001> direction. Furthermore, photocurrent-potential (I-V) curves show that the solar cells fabricated with the SNS collected after 18 h hydrothermal treatment (SNS-18) exhibit the highest solar energy conversion efficiency. The efficiency is improved by 24.5% compared with that of the cells fabricated with pure P25. Based on the UV-Vis spectrum, nitrogen sorption and IPCE analysis, the improved performance can be attributed to the enhanced scattering and increased active sites for dye loading. Therefore, the dual functions of light scattering and many active sites for dye loading make SNS superior candidates for DSSCs.