A quasi-solid-state electrolyte employing a poly (ethylene oxide)/LiI system without a filler is evalued. The electrolyte is optimized for various potassium iodide (KI) concentrations. The electrolyte containing 14.5 wt.% KI exhibits the hightest conductivity (3.0 x 10(-3) S cm(-1)). An efficiency of 4.5T is achieved using this composition of the electrolyte. It is shown that the introduction of KI in a conventional PEO/I-2/LiI electrolyte system prevents the crystallization of the polymer matrix and enhances the ionic conductivity. The energy conversion efficiency of the device is further enhanced to 5.8% by incorporating a light-scattering layer. (C) 2010 Elsevier B.V. All rights reserved.