Transparent Platinum Counter Electrode for Building Integrated Dye-Sensitized Solar Cells
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Transparent Platinum Counter Electrode for Building Integrated Dye-Sensitized Solar Cells Anastasiia Iefanova1, Mahdi Farrokh Baroughi1, Daren Davoux1, Umesh Gautam1, Dilip Dachhepati1, and Jeevan Nepal1 1 Department of Electrical Engineering and Computer Science, South Dakota State University, Brookings, SD-57007, USA ABSTRACT A new type of counter-electrode based on platinum (Pt) nanoclusters has been introduced for semi-transparent dye-sensitized solar cells (DSSCs). This electrode is fabricated using a drop coating method where Pt nanoparticles dispersed in an acetone solvent are applied on a heated indium tin oxide (ITO) coated glass substrate. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) images suggest that the Pt nanoparticles form a nanoporous structure with a large surface area while the distribution of Pt appears to be uniform on the surface of the ITO layer. UV/visible/near infrared transmittance spectroscopy showed that the Pt/ITO/glass electrode is highly transparent with a maximum transparency of 80% at 550 nm. INTRODUCTION DSSCs have a potential to provide various degree of transparency, which makes them suitable for building window applications. The objective of this work is focused on developing highly transparent counter-electrode (CE). The role of the CE in DSSCs is to inject low energy electrons into electrolyte through a reduction process. The main requirements for the materials used as CE for DSSC are a low charge-transfer resistance and high catalytic properties for the reduction of oxidized electrolyte species. Counter-electrodes for DSSCs must also be chemically and electrochemically stabile in an electrolyte medium. It is known that the available effective surface area of the counter-electrode constitutes an important role in the overall electric current within the device. It is necessary to fabricate rough and porous counter electrodes in order to maximize the surface area, resulting in a higher density of catalytic sites. Acting as a catalyst, platinum is commonly used in CEs for DSSCs to catalyze the reduction of triiodide to iodide in the electrolyte system. Besides platinum, carbon materials, conductive organic polymers, and inorganic materials have been investigated to fabricate counter-electrode for DSSCs. Nevertheless, Pt is still the best candidate for counter-electrode material because of its high electrical conductivity, high electrocatalytic affinity towards reduction of triiodide to iodide, and its light reflecting properties. Up till now, the best counter-electrode developed for DSSCs was a platinum film sputtered on TCO-coated glass substrate. However, this type of counter electrode is not appropriate for window application since it is not transparent and requires a large amount of platinum. The chemical reduction (calcination) method has been used to fabricate counter-electrode for transparent DSSCs by spin-coating an H2PtCl6 solution on TCO-glass substrate, followed by heat treatment [1-4]. Compared to the one prepared by sputtering method, the Pt co
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