Enhancing Quasi Solid-state Dye-sensitized Solar Cell Performance Using Mixed-polymer Gel Electrolytes: the Influence of Low and High Molar-weight Polymers

Abstract Gel polymer electrolytes (GPEs) are crucial in quasi solid-state dye-sensitized solar cells (DSSCs) due to their chemical and physical stability, enhanced safety, and improved performance, which boosts ionic conductivity. This study presents the enhancing gel polymer electrolyte properties intended for DSSCs by blending low and high-molar weight variants of the same polymer. Using the hot press method, the synthesized polymer blend electrolyte shows notable DSSC performance improvement. The blend incorporates polyethylene oxide (PEO, MW 4,000,000) and its lower molar weight counterpart, polyethylene glycol (PEG, MW 4,000). The ionic conductivities of the GPEs were assessed via impedance analysis. The GPE with 100% PEG achieved the highest ionic conductivity (10.30 mS cm⁻ ¹) but was liquid-like, while 100% PEO showed the lowest conductivity (5.23 mS cm⁻ ¹) with a solid-state nature. A blend with a 3:1 PEO to PEG ratio exhibited intermediate conductivity and a gel-like consistency. Utilizing this electrolyte in solid-state DSSCs yielded an extremely high 8.76% power conversion efficiency and a short-circuit current density of 13.80 mA cm⁻ ². The lowest efficiency was observed for the 100% PEO content. The study demonstrated a significant efficiency improvement of 38.17% and 36.45% in blend polymer electrolyte-based DSSCs compared to single polymer electrolytes with PEO and PEG, respectively. Conductivity in the GPEs followed Vogel-Tamman-Fulcher behavior. The DSSCs utilized N719 dye-sensitized TiO₂ nanoparticle multi-layer photoanodes and Pt counter electrodes. The results indicate that combining low and high-molar-weight polymers in the electrolyte significantly boosts DSSC efficiency. Current efforts aim to refine polymer composition and understand the mechanisms behind the efficiency enhancement in mixed-phase gel polymer electrolytes.