Comparative Study on the Photovoltaic Properties of Dye-Sensitized Solar Cells (DSCs) Based on Different Counter Electrode Configurations

Previously, we reported an investigation on Delonix regia dye extract as a natural sensitizer for TiO2/DSC assembled with platinum counter electrode and low power conversion efficiency was recorded. This necessitated the current investigation on Delonix regia dye extract as a natural sensitizer for TiO2/DSCs assembled with different counter electrodes. Platinum counter electrode was used for one of the DSCs while polyaniline (PANI) was used to replace platinum in the other DSC. The vitriol treated PANI thin film consisted of aniline mixed with potassium dichromate directly reacted on circular graphite foam. The conductivity and Hall coefficient were measured to be and respectively using ECOPIA Hall Effect Measurement System (HMS-3000 Version 3.52). Sequel to this, the DSCs were assembled and characterized using a standard overhead Veeco viewpoint solar simulator equipped with AM 1.5 filter to give a solar radiation of 1000 W/m2 and coupled to a Keithley source meter (model 4200SCS) which was connected to the computer via GPIB interface for data acquisition. The overall solar power conversion efficiencies of 0.02% and 0.04% were obtained for TiO2-DSC//Delonix regia dye//platinum electrode and TiO2-DSC//Delonix regia dye//PANI electrode respectively. Delonix regia dye extract proved to be rather a poor sensitizer as can be seen by the low spectral absorption at lower energies with short circuit current density of 0.10mAcm-2 and 0.11mAcm-2 respectively. Nevertheless, a 10% decrease in the electron recombination via redox electrolyte and collection at the photoelectrode was observed for TiO2-DSC//Delonix regia dye//PANI electrode and a 20% increase in the open circuit voltage (Voc) was also observed. Finally, about 37% increase in the fill factor was observed for the TiO2-DSC//Delonix regia dye//PANI electrode over TiO2-DSC//Delonix regia dye//platinum electrode. This necessitated approximately 50% increase in the power conversion efficiency for the TiO2-DSC//Delonix regia dye//PANI electrode over TiO2-DSC//Delonix regia dye//platinum electrode.