Tetrahexylammonium Iodide Containing Solid and Gel Polymer Electrolytes for Dye Sensitized Solar Cells

Abstract

TiO2 dye sensitized solar cells (DSSCs) are emerging as an alternative technology to photovoltaic junction devices. DSSCs conventionally use liquid-type electrolytes but solid and gel polymer electrolytes are more promising due to many advantages. However, their conductivity needs to be enhanced in order to make them useful in practical device applications. In this work, an iodide ion conducting polymer electrolyte was prepared using polyacrylonitrile (PEO), tetrahexylammonium iodide salt with ethylene carbonate and propylene carbonate plasticisers. The salt composition was varied to find the optimum conductivity. The sample containing 120% salt with respect to PEO weight showed the highest conductivity. This optimum electrolyte showed a glass transition at -102.3°C and an ambient temperature conductivity of 2.1×10-3 S cm−1 at 30°C. The optimized gel electrolyte was used in a quasi solid-state DSSC and a ISC of 9.37 mA cm-2, a VOC of 696 mV and an efficiency of 2.8% were achieved under irradiation of 1000 W m−2. In addition, a solid polymer electrolyte was fabricated using the same salt with polyethylene oxide host polymer and ethylene carbonate. The salt composition was varied to obtain the highest conductivity and the best performing sample with composition 65% salt with respect to PEO weight showed a conductivity of 4.7×10-4 S cm-2 at 30°C. This electrolyte was used in a DSSC and it showed a ISC of 1.26 mA cm-2, a VOC of 745 mV and efficiency of 0.6%.