Tailoring of nanoporous TiO2 spheres with 100–200 nm sizes for efficient dye-sensitized solar cells

Abstract Highly porous and monodispersed TiO 2 spheres (SPs) with diameters in the range of 100–200 nm, notably smaller than the conventional SPs reported thus far, were selectively controlled, and found to be an outstanding building block for the mesoporous TiO 2 layer in dye-sensitized solar cells (DSCs). The prepared TiO 2 films employing these SPs are highly transparent, and the fabricated DSCs exhibit significantly enhanced photovoltaic performances. Particularly, the 100 nm-sized TiO 2 SP (SP100) provides a photovoltaic conversion efficiency (PCE) of 10.66% with a J SC of 17.98 mA/cm 2 , V OC of 808 mV, and FF of 0.734, which is higher than the PCE of DSCs with the typical 20 nm-sized TiO 2 nanoparticle (NP20) or conventional 250 nm-sized SP (SP250). Transient photoelectron spectroscopic analyses revealed that both the electron diffusion coefficient and electron lifetime of the TiO 2 layer increase as the size of the SPs decreases. The tiny TiO 2 SPs prepared in this work offer distinct advantages in electron transport as well as dye-soaking and electrolyte diffusion.