Dependence of the electrocatalytic performance of platinized counter electrodes on the redox mediator employed in dye-sensitized solar cells
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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 Ω cm2 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.
KeywordsElectrocatalyst Counter electrode Dye-sensitized solar cell
This work was supported by a grant from Korea Electrotechnology Research Institute (KERI) and the “New & Renewable Energy Core Technology Program” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 2011T100100678).
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