Performance enhancement of dye-sensitized solar cells using nanostructural TiO2 films prepared by a graft polymerization and sol-gel process

Nanostructural TiO2 films with large surface areas were prepared by the combined process of graft polymerization and sol-gel for use in dye-sensitized solar cells (DSSCs). The surface of the TiO2 nanoparticles was first graft polymerized with photodegradable poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization (ATRP), after which the particles were deposited onto a conducting glass. The PMMA chains were removed from the TiO2 films by UV irradiation to generate secondary pores, into which titanium isopropoxide (TTIP) was infiltrated. The TTIP was then converted into small TiO2 particles by calcination at 450 oC, as characterized by energy-filtering transmission electron microscopy (EF-TEM) and field emission scanning electron microscopy (FE-SEM). The nanostructural TiO2 films were used as a photoelectrode in solid-state DSSCs; the energy conversion efficiency was 5.1% at 100 mW/cm2, which was higher than the values achieved by the pristine TiO2 (3.8%) and nongrafted TiO2/TTIP photoelectrodes (3.3%). This performance enhancement is primarily due to the increased surface area and pore volume of TiO2 films, as revealed by the N2 adsorption-desorption isotherm.