High efficiency solid state dye sensitized solar cells with graphene–polyethylene oxide composite electrolytes

Abstract

Novel and highly effective composite electrolytes were prepared by combining the two dimensional graphene (Gra) and polyethylene oxide (PEO) for the solid electrolyte of dye sensitized solar cells (DSSCs). Gra sheets were uniformly coated by the polymer layer through the ester carboxylate bonding between oxygenated species on Gra sheets and PEO. The Gra–PEO composite electrolyte showed the large scale generation of iodide ions in a redox couple. From rheological analysis, the decrease in viscosity after the addition of LiI and I₂ in the Gra–PEO electrolyte might be explained by the dipolar interactions being severely disrupted by the ionic interactions of Li⁺, I⁻, and I₃⁻ ions. A composite electrolyte with 0.5 wt% Gra presented a higher ionic conductivity (3.32 mS cm⁻¹) than those of PEO and other composite electrolytes at room temperature. A high overall conversion efficiency (∼5.23%) with a very high short circuit current (J_SC) of 18.32 mA cm⁻², open circuit voltage (V_OC) of 0.592 V and fill factor (FF) of 0.48 was achieved in DSSCs fabricated with the 0.5 wt% Gra–PEO composite electrolyte. This enhanced photovoltaic performance might be attributed to the large scale formation of iodide ions in the redox electrolyte and the relatively high ionic conductivity.