Effect of Particle Size on the Performance of TiO₂ Based Dye-Sensitized Solar Cells

The performance of TiO₂ based dye-sensitized solar cells (DSSCs) is largely influenced by the size of the TiO₂ particles. In this work, different-sized TiO₂ nanoparticles have been synthesized by a facile sol–gel technique using polyethylene glycol (PEG) as capping agent and its performance as the photoanode of DSSC with N719 sensitizer dye is investigated. Particle nature and dimension of TiO₂ nanoparticles were studied through XRD, FTIR, SEM and dynamic light scattering (DLS) analyses, whereas thermal stability was investigated through TGA in the temperature range of 30–600 °C 30–600 ^°C. The DSSC assembled with photoanode consisted of smallest size TiO₂ nanoparticles obtained using 3 mM PEG (TNP-II) exhibited solar-to-electrical energy conversion efficiency of 2.5%, under illumination of 100 mWcm⁻², which was an extensive improvement compared to the device based on un-capped, TiO₂ nanoparticles based cell (TNP) (1.0%). The enhancement in efficiency resulting from the reduction of particles size of TiO₂ is attributed to enlarged band-gap, increased specific surface area & surface to volume ratio of the photoanode, greater dye loading and more interactions between anchoring groups of the dye and surface of TiO₂.EIS measurements revealed that TNP-II photoanode–based cells exhibited faster electron transport, increased electron lifetime, higher charge collection efficiency and less recombination leading to better photovoltaic output. The work shows that developed TNP-II nanoparticles have good potential for application in photoenergy conversion devices.