Efficiency enhancement in dye-sensitized solar cells fabricated with poly(ethylene oxide) based solid polymer electrolyte mediated by the mixed cation and nano filler effects

Journal article, 2026

The use of volatile liquid electrolytes in dye-sensitized solar cells (DSSCs) hinders their large-scale commercialization. In this regard, DSSCs based on solid polymer electrolytes or gel polymer electrolytes have emerged as devices offering improved stability and enhanced efficiency. In this work, solid and gel polymer electrolytes based on poly(ethylene oxide) (PEO) were explored in conjunction with the mixed cation iodide salts (tetrapropylammonium iodide and potassium iodide), and TiO₂ nanofillers. DSSCs sensitized with N719 dye were fabricated with these materials, and their performance was evaluated. The PEO-based solid polymer electrolyte containing 15 wt% Pr₄N⁺I⁻ exhibited the highest ionic conductivity of 3.97 × 10⁻⁵ S·m⁻¹ and the DSSC power conversion efficiency (PCE) of 1.08%. The incorporation of 42.5 wt% of the solid plasticizer, ethylene carbonate (EC) increased the amorphous phase content in the PEO electrolyte and improved the iodide ion transport, enhancing the solar cell efficiency to 1.46%. Further enhancement in efficiency to 1.81% was achieved by incorporating two iodide salts with mixed cations (Pr₄N⁺ and K⁺), benefiting from the synergistic “mixed cation effect”. Incorporating 2.5 wt% TiO₂ nanofiller further boosted the PCE to 3.02% due to the nanofiller effect. TiCl4 surface treatment of the TiO₂ photoanode substantially enhanced the DSSC efficiency to 3.41%.