Performance Enhancement of sp2 Carbon Incorporated Polymer Gel Electrolyte in Dye-sensitized Solar Cell

Different dimensional carbon materials, including multi-walled carbon nanotubes (MWCNT, one dimensional (1D)), graphene (two dimensional (2D)), and carbon black (zero dimensional (0D)), could be successively dispersed by an excellent home-made dispersant, namely poly(oxyethylene)-segmented imide (POE-segmented imide, POEM). The dispersibilities of the carbon materials in POEM were verified by UV-vis spectroscopy and transmission electron microscopy (TEM). The carbon materials (with the POEM) were then incorporated in an elastomer of poly(oxyethylene)-segmented amide-imide (POE-PAI), which was synthesized by the polymerization of poly(oxyethylene)-segmented diamine and 4,4-oxydiphthalic anhydride (ODPA). The carbon-incorporated polymer gels were used as quasi-solid-state electrolytes for dye-sensitized solar cells (DSSCs). The chemical structure of POE-PAI was characterized by Fourier transform infrared spectroscopy (FTIR). The DSSCs with graphene and MWCNT exhibited much higher power conversion efficiencies (η, 7.96% and 7.90%, respectively), compared to that of the DSSC with pristine POE-PAI as the polymer gel electrolyte (PGE, 7.32%); these enhanced η’s can be attributed to the higher ionic conductivities of the electrolytes with graphene and carbon nanotubes. Electrochemical impedance spectra and conductivity data are used to support these photovoltaic parameters. Furthermore, morphologies of the elastomers of these polymer gel electrolytes are found to play important roles in deciding the η’s of the pertinent DSSCs; these morphologies are examined through scanning electron microscope (SEM) images. The best power conversion efficiency (7.96%) obtained in this research is much better than most of the η’s obtained hitherto for quasi-solid state DSSCs.