Effect of aging conditions on the performance of dip coated platinum counter electrode based dye sensitized solar cells

Abstract

Platinum is the most widely accepted excellent catalytic material for counter electrodes in dye sensitized solar cells (DSSCs). The problems associated with platinum are high cost and low corrosion resistance against the iodide/triiodide redox couple. Use of platinum nanoparticles for counter electrodes resolves the cost issue. The present work shows the effect of different aging conditions on the performance of DSSCs fabricated using platinum nanoparticle based counter electrodes. Two conditions – room temperature under darkness (R-D) and heating (60 °C) under illumination (H-I) – were chosen for the aging studies. Platinum nanoparticles with a size of ∼2 nm were synthesized and a dip coating process was followed to fabricate counter electrodes. Electrolyte (iodide/triiodide) and counter electrode interaction were studied by fabricating symmetric cells composed of two platinized electrodes. It was found that platinum almost entirely reacted with the electrolyte within 51 days for the H-I condition aged symmetric cell, whereas R-D condition aging was relatively ineffective in the dissolution of platinum. Interestingly, in DSSCs aged under the H-I condition for 3 months, photoconversion activity was still observed, which was later attributed to the presence of platinum on the counter electrode. So, in short circuit conditions under illumination, the dissolution of platinum by the electrolyte is delayed. The R-D condition aged cell showed a smaller decrease in performance compared to the H-I condition aged cell. Other components of the DSSCs such as titania film and dye were also characterized. Finally, it was found that apart from dissolution of platinum from the counter electrode, desorption of additives or ions of electrolyte from titania are also responsible for the decay in DSSC performance with aging.