Mixed cation effect and iodide ion conductivity in electrolytes for dye sensitized solar cells

• Published in: Ionics Vol. 23; no. 10; pp. 2901 - 2907
• Main Authors: Lakshman Dissanayake, M. A. K., Senadeera, G. K. R., Bandara, T. M. W. J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2017; Springer Nature B.V
• Subjects: Cations; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Dye-sensitized solar cells; Dyes; Electrochemistry; Electrolytes; Electrolytic cells; Energy conversion efficiency; Energy Storage; Low cost; Optical and Electronic Materials; Original Paper; Photovoltaic cells; Polyacrylonitrile; Polyethylenes; Polymers; Polymethyl methacrylate; Renewable and Green Energy; Short circuits; Solar generators; Mixed cation effect; Dye sensitized solar cells; Iodide ion conductivity
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-016-1902-z

Dye-sensitized solar cells (DSSCs) offer an alternative to conventional silicon solar cell because of low cost and easy fabrication. However, one major drawback in DSSCs is their low efficiency. This paper reports the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells based on polymer gel electrolytes. Several different polymers, such as polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), poly (vinylidenefluoride (PVdF)), and polyethylene oxide (PEO) have been used as host polymers. A binary iodide mixture consisting of an alkaline iodide salt (small cation) and a quaternary ammonium iodide salt such as tetrapropyl ammonium iodide (Pr 4 NI) (large cation) has been used as the iodide ion source. In some of these systems, efficiency enhancement of more than 25% has been reached due to the “mixed cation effect”. From these studies, it was established that the variation of the power conversion efficiency with the concentration ratio of the two iodide salts follows the same trend as the short circuit current density ( J sc ) and goes through a maximum at a particular salt concentration ratio. The maximum efficiency was found to be higher than the efficiencies of the DSSCs with only a single iodide salt in the electrolyte. The J sc in these DSSCs appears to be governed by the iodide ion conductivity of the gel electrolyte. The observed efficiency enhancement has been explained on the basis of the electrode effects as well as electrolyte effects where the cations play a dominant role.