Cr-doped TiO2-based dye-sensitized solar cells with Cr-doped TiO2 blocking layer

Cr-doped TiO2 nanoparticles were synthesized by chemical sol-gel method. The anatase phase of TiO2 nanoparticles was proved by X-ray diffraction analysis. Furthermore, the field emission scanning electron microscopy revealed that the size of the nanoparticles was about 30 nm. TiO2 nanoparticles with 0.5 % Cr dopant concentration were selected to fabricate dye-sensitized solar cells due to their smaller band gap. Furthermore, Cr-doped TiO2 thin films (0.5 %) with different thicknesses were employed as blocking layer on the surface of fluorine-doped tin oxide (FTO) substrate. The current density-voltage measurement showed that the photovoltaic parameters of the fabricated dye-sensitized solar cells were improved after introducing Cr-doped TiO2 blocking layer at the interface of FTO and Cr-doped TiO2 mesoporous layer. The maximum power conversion efficiency increased more than 110 % as a result of inserting the Cr-doped blocking layer. The electrochemical impedance spectroscopy indicated that a more efficient charge transfer process takes place at the interface of the FTO/TiO2 due to the enhanced interfacial properties and reduction of charge recombination.