Electrochemical Impedance Model of a (Low-cost) Dye-Sensitized Solar Cell

• Main Authors: R. Cisneros, M. Beley, F. Lapicque
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2014-10-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/5215

Dye-sensitized solar cells (DSSCs) have been considered as a potential efficient tool for conversion of solar energy to electricity. DSSC’s rely upon the presence of a semi-conductor (e.g. TiO2) attached to the photoanode and a sensitizer (dye) for photogeneration of electrons at the SC interface. Most efficient DSSC’s are based on Ru-organic coordination complexes as sensitizer, however the finite availability of Ru led to search for other dyes, being organic molecules or other metal-coordination complexes. The efficiency of the cell can be greatly affected by recombination of generated electrons by several processes in the cell, so co-adsorbents – organic molecules – can be added to the dye to hinder recombination of the electrons by shielding the TiO2 surface. The present investigation deals with an impedance model tested for the case of a Ru-free organic sensitizer in the presence of one co-adsorbent amongst three different molecules at various concentrations. Best performances of the cell evaluated by i-V curves and impedance spectroscopy have been observed for co-adsorbent/dye ratio near 0.1, but in most cases, addition of the co-adsorbent was shown to improve both the exchange current density for electron collection at the anode and that of recombination phenomena, which contradicts the usual belief.