Preparation and characterization of core-shell electrodes for application in gel electrolyte-based dye-sensitized solar cells

Core-shell electrodes based on TiO2 covered with different oxides were prepared and characterized. These electrodes were applied in gel electrolyte-based dye-sensitized solar cells (DSSC). The TiO2 electrodes were prepared from TiO2 powder (P25 Deguissa) and coated with thin layers of Al2O3, MgO, Nb2O5, and SrTiO3 prepared by the sol-gel method. The core-shell electrodes were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy measurements. J-V curves in the dark and under standard AM 1.5 conditions and photovoltage decay measurements under open-circuit conditions were carried out in order to evaluate the influence of the oxide layer on the charge recombination dynamics and on the device's performance. The results indicated an improvement in the conversion efficiency as a result of an increase in the open circuit voltage. The photovoltage decay curves under open-circuit conditions showed that the core-shell electrodes provide longer electron lifetime values compared to uncoated TiO2 electrodes, corroborating with a minimization in the recombination losses at the nanoparticle surface/electrolyte interface. This is the first time that a study has been applied to DSSC based on gel polymer electrolyte. The optimum performance was achieved by solar cells based on TiO2/MgO core-shell electrodes: fill factor of similar to 0.60, short-circuit current density J(sc) of 12 mA cm(-2), open-circuit voltage & of 0.78 V and overall energy conversion efficiency of similar to 5% (under illumination of 100 mW cm(-2)). (C) 2009 Elsevier Ltd. All rights reserved.