Hierarchical TiO ₂ spheres architectures for quasi solid state dye-sensitized solar cells by living radical polymerization and sol-gel process

Titanium dioxide (TiO ₂) photoelectrode is one of the most important components in a dye-sentisized solar cell (DSSC). In common, the overall performance of the DSSC depends on the surface area of the TiO ₂ photoelectrode which is directly correlated to the amount of dye loading. Dye loading increased with the increase in the surface area of TiO ₂ layer that enhanced short circuit current (J _sc) performance in DSSC. In addition, for better penetration of electrolytes, it is essential to use the mesoporous or macroporous TiO ₂ photoelectrode structure than microporous TiO ₂ photoelectrode structure. The photoelectrode made up of from commercially available TiO ₂ (P25, Degussa) has limitations mainly because of lower surface area which motivated us to modify it by atom transfer radical polymerization (ATRP) process with hydrophilic poly(ethylene glycol) methyl ether methacrylate (POEM). Dye-sensitized solar cells (DSSCs) made from TiO ₂ spheres with hierarchical pores exhibited improved photovoltaic efficiency (3.30% for low molecular weight (M _w) and 2.50% for high M _w polymer electrolytes), as compared to those from pristine TiO ₂ nanoparticles (2.40% for low M _w and 1.30 % for high M _w) at 100 mW/cm ², due to the increased surface areas and light scattering.