Hierarchical TiO2 spheres architectures for quasi solid state dye-sensitized solar cells by living radical polymerization and sol-gel process

Titanium dioxide (TiO₂) 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 TiO₂ photoelectrode which is directly correlated to the amount of dye loading. Dye loading increased with the increase in the surface area of TiO₂ 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 TiO₂ photoelectrode structure than microporous TiO₂ photoelectrode structure. The photoelectrode made up of from commercially available TiO₂ (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 TiO₂ 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 TiO₂ nanoparticles (2.40% for low M_w and 1.30 % for high M_w) at 100 mW/cm², due to the increased surface areas and light scattering.