Cross-linked gel polymer electrolyte containing multi-wall carbon nanotubes for application in dye-sensitized solar cells

A cross-linked gel polymer electrolyte composed of poly (ethylene oxide-co-2-(2-methoxyethoxy) ethyl glycidyl ether-co-allyl glycidyl ether, gamma-butyrolactone, LiI and I-2, mixed with functionalized multi-wall carbon nanotubes (MWCNT), was applied in dye-sensitized solar cells (DSSC). The electrolyte was characterized by differential scanning calorimetry, conductivity measurements and Raman spectroscopy. Due to its nature, the terpolymer was chemically cross-linked during DSSC assembly to give rise to quasi-solid state solar cells. The gel polymer electrolyte containing 1 wt% of MWCNT exhibited conductivity values higher than 10(-3) S cm(-1). An increase in MWCNT content provided a smaller concentration of polyiodide species, as confirmed by Raman spectroscopy. The highest photocurrent (8.74 mA cm(-2)) was achieved by DSSC based on the cross-linked gel polymer electrolyte containing 1 wt% of MWCNT compared to DSSC based on non-cross-linked gel polymer electrolytes (7.93 mA cm(-2)). The incorporation of 3 wt% of MWCNT into the gel polymer electrolyte promoted a decrease in both J(sc) and V-oc, probably due to poorer light transmittance of the electrolyte in the visible range and higher charge recombination losses, respectively. Thus, the highest efficiency in this work was achieved by using electrolyte containing 1 wt% of MWCNT. After the cross-linking process, the dimensional stability of the gel composite electrolyte was improved and the conversion efficiency of DSSC was only slightly affected, changing from 3.37% (before cross-linking) to 3.35%. (C) 2012 Elsevier B.V. All rights reserved.