Synthesis and characterization of Nb-La co-doped TiO2 nanoparticles by sol-gel process for dye-sensitized solar cells

One of the main challenges of the current photovoltaic systems is improving the performance of the dye-sensitized solar cells (DSSCs). The deliberate insertion of impurity ions into the TiO2 crystal lattice as an electron transporting material in DSSCs might be an effective method for improving the electronic properties of TiO2, which leads to enhancing the photovoltaic efficiency. Recently, co-doping has become a promising strategy that can be used for effective tuning of the electronic properties. In the present study, this method was applied as a novel approach to synthesize Lanthanum-Niobium(La,Nb)-codoped TiO2 nanocrystals via the Pechini sol-gel technique. According to the results, the x-ray diffraction investigation approved the anatase phase formation of (Nb-La)-codoped TiO2 nanoparticles. In addition, the field-emission scanning electron microscopy (FESEM) showed the nanoparticles were semi-spherical and approximately 30 nm in size. The photovoltaic parameters of the assembled dye-sensitized solar cells were tested via current density-voltage measurement, exhibiting an enhancement through introducing 2% mol Nb-La ions into the TiO2 crystal lattice. The electrochemical impedance spectroscopy showed that the charge transfer process occurred faster at the FTO/TiO2 interface, which was attributed to the reduction of charge recombination and enhanced electron conductivity.