Bis-imidazolium based poly(ionic liquid) electrolytes for quasi-solid-state dye-sensitized solar cells

Bis-imidazolium based poly(ionic liquid), poly(1-butyl-3-(1-vinylimidazolium-3-hexyl)-imidazolium bis(trifluoromethanesulfonyl)imide) (Poly[BVIm][HIm][TFSI]) and mono-imidazolium based poly(ionic liquid), poly(1-butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (Poly[BVIm][TFSI]), were synthesized and dissolved in room temperature ionic liquids (ILs) to form quasi-solid-state electrolytes for dye-sensitized solar cells (DSSCs), without using any volatile organic solvent. Compared with mono-imidazolium based poly[BVIm][TFSI], bis-imidazolium based poly[BVIm][HIm][TFSI] electrolytes showed a higher thermal stability and conductivity due to the charge transport networks formed in the gel electrolytes via the π–π stacked imidazolium rings. The DSSCs based on the poly[BVIm][HIm][TFSI] gel electrolyte showed a superior long-term stability and yielded a power conversion efficiency of 5.92% under the simulated air mass 1.5 solar spectrum illumination at 100 mW cm−2. This study offered a feasible method to fabricate quasi-solid-state DSSCs in future practical applications.