Propertv of palladium counter electrode for dye sensitized solar cells

Palladium (Pd) nano films were deposited at different thicknesses of 34, 46, and 90 nm by sputtering for use as the counter electrode (CE) in dye sensitized solar cell (DSSC). Conventional Pt layers were also prepared using the same process for comparison. Finally 0.45 cm² DSSCs employing the Pd or R CE were prepared, and their photovoltaic properties and microstructure were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), current-voltage (l-V), and transmission electron microscopy (TEM) characterization. CV showed that the catalytic activity of Pd was lower than that of R. Moreover, the catalytic activity of Pd increased with increasing thickness. Impedance analysis revealed huge charge transfer resistance at the Pd interface that decreased with increasing Pd thickness. R showed low resistance without a thickness dependence. The l-V result of the DSSC device employing Pd and R revealed a mean energy conversion efficiency of 4.32% and 6.57%, respectively. TEM showed that the Pd films were not deposited conformally compared to R films. The uneven microstructure of the Pd film can lead huge interface resistance and low efficiency. These results suggest that Pd can be used as the counter electrode in DSSCs instead of conventional R but the Pd film uniformity needs to be improved.