Size-controlled synthesis of mesoporous Nb2O5 microspheres for dye sensitized solar cells

Mesoporous Nb2O5 microspheres assembled by nanoparticles are successfully synthesized through a simple solvothermal process and subsequently annealing treatment, free of any template or catalyst. By controlling the reactant NbCl5 concentration, we could easily tune the diameter of the Nb2O5 spheres from 200 to 900 nm, which were also used to fabricate dye-sensitized solar cells. Studies found that dye-sensitized solar cells based on Nb2O5 with sizes of around 480 nm show a highest power conversion efficiency of 2.97% with a relatively high short current density (Jsc) of 6.8 mA cm−2 and an open circuit voltage (Voc) of 0.738 V, which benefits from its higher specific surface area for adsorbing more dye molecules, superior light scattering capacity for boosting the light-harvesting efficiency, and modest electron transport properties.