The electrocatalytic properties of platinized counter electrodes (Pt CEs) prepared by various coating methods were investigated with respect to the redox mediator, including the widely used iodide/tri-iodide (I-/I (3) (-) ) and the more recently introduced cobalt(II/III)tris(2,2'-bipyridine) (Co(bpy) (3) (2+/3+) ), for application in dye-sensitized solar cells (DSCs). The coating methods controlled Pt loading and the surface morphology of the Pt CEs. For a high-performance DSC with a fill factor > 0.7, the charge-transfer resistance at the Pt CE/electrolyte interface should be < 4.5 Omega cm(2) for both redox mediators. The I-/I (3) (-) -mediated DSCs were insensitive to Pt loading as low as 0.001 mg cm(-2), while the Co(bpy) (3) (2+/3+) -mediated DSCs required relatively large Pt loadings of > 0.005 mg cm(-2). Our results indicated that care should be taken in the preparation of Pt CEs with high transparency and low loading to obtain high-performance DSCs employing cobalt-ligand redox electrolyte.