Rutile TiO2 microspheres with exposed nano-acicular single crystals for dye-sensitized solar cells

Uniquely structured rutile TiO2 microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 °C for 2 h, the rutile TiO2 microspheres with a high surface area of 132 m2/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells (DSSCs). The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO2 photoanodes made of rutile TiO2 microspheres and anatase TiO2 nanoparticles (mass ratio of 1:1), significantly higher than that of pure anatase TiO2 nanoparticle photoanodes of similar thickness (6.74%). Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of rutile TiO2 microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes (450–800 nm) to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular rutile single crystals phases giving high electron collection efficiency. [inline-graphic not available: see fulltext]