Synthesis of mesoporous TiO2 spheres and aggregates by sol–gel method for dye-sensitized solar cells

• Mesoporous TiO2 spheres and TiO2 aggregates were synthesized.
• The cell efficiency of TiO2 sphere electrode increased by F127 addition.
• Mesoporous TiO2 aggregate electrode exhibited the best solar cell performance.
• High crystallinity was important to improve the photovoltaic properties.
• Large pore size of TiO2 aggregates was also the positive factor.

Mesoporous microspheres of anatase TiO2 were synthesized by hydrolysis of titanium butoxide in butanol. The TiO2 micospheres were about 0.5 μm in size, composed of primary nanoparticles of about 10 nm, and the specific surface area increased by addition of triblock copolymer (Pluronic F127). TiO2 aggregates with irregular shape were formed by hydrothermal treatment. Before and after calcination, the crystallinity of TiO2 aggregates was high although the specific surface area decreased. The cell efficiency of TiO2 sphere electrode increased by F127 addition. Furthermore, TiO2 aggregate electrode exhibited an efficiency of 5.6%, which was much higher than those of TiO2 spheres with F127 and commercial TiO2 nanoparticles (P25) electrodes. It was confirmed that the high crystallinity of TiO2 was important to improve the photovoltaic properties as well as large surface area.

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