Dye-Sensitized Solar Cells for Ruthenium Counter Electrodes Employing Polystyrene Beads and ZnO

In order to improve the energy conversion efficiency (ECE) by increasing the surface area of counter electrode (CE), we prepared 500 nm-polystyrene (PS) beads on a flat glass substrate, deposited with 100 nm-thick ZnO and 34 nm-thick Ru nano thin film using ALD. A 34 nm-thick Ru CE on a flat glass substrate was also prepared using the same method for a comparison. Finally, a 0.45 cm(2) dye-sensitized solar cell (DSSC) device with a glass/FTO/blocking layer/TiO2/N719(dye)/electrolyte/34 nm-Ru/100 nm-ZnO/500 nm-PS bead/glass structure was fabricated. The microstructure of the CE was examined by field emission scanning electron microscopy (FE-SEM). The photovoltaic properties, such as the short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), energy conversion efficiency (ECE) and impedance, were characterized using a solar simulator and potentiostat. The microstructure examined using a FE-SEM confirmed that 100 nm-ZnO/34 nm-Ru on 500 nm-PS beads increases the surface area by 70% compared to a glass substrate. The ECE of the device with the CE, the glass/Ru and 500 vnm-beads/100 vnm-ZnO/Ru, was 1.81%, and 2.91%, respectively. These results suggest that the surface area of the CE contributed to the increase in efficiency. Moreover, increasing of surface area through ZnO coating on PS beads was more suitable for increasing efficiency than the conventional flat glass substrates.