Synthesis and application of PEGBEM-g-POEM graft copolymer electrolytes for dye-sensitized solar cells

• PEGBEM–POEM comb copolymer is synthesized via facile free radical polymerization.
• Addition of MPII reduces the degree of crystallinity and increases chain flexibility.
• Distinct structural amphiphilic properties are observed by AFM and SAXS analysis.
• Efficiencies of graft copolymer-based DSSCs are higher than homopolymer-based cells.
• This improved performance mostly results from the increased ionic conductivity.

We report a nanostructural amphiphilic graft copolymer electrolyte based on poly(ethylene glycol) behenyl ether methacrylate (PEGBEM) and poly(oxyethylene methacrylate) (POEM) synthesized via a facile free radical polymerization. The synthesis of PEGBEM-g-POEM graft copolymers, and its interaction with an ionic liquid (i.e., 1-methyl-3-propylimidazolium iodide (MPII)), were confirmed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM). The addition of MPII reduced the degree of crystallinity of the graft copolymer, resulting in improved ionic conductivity up to 1.4 × 10−6 S/cm at 25 °C. The efficiency of dye-sensitized solar cells (DSSCs) with this graft copolymer electrolyte (3.6%) was higher than those of DSSCs with homopolymer electrolytes (2.3 to 2.5%), indicating the effectiveness of the nanostructural graft copolymer. The higher efficiency resulted from an improved current density (Jsc) due to enhanced polymer flexibility and reduced crystallinity.