Solid electrolyte-based on lithium iodide (LiI) and 3-hydroxypropionitrile (HPN) for dye-sensitized solar cells (DSSCs) has been synthesized. Fourier transform infrared, ac impedance spectroscopy, and differential scanning calorimetry are employed to characterize the properties of the composite. Its conductivity increases with decreasing LiI content. Maximum conductivity of 3.1 x 10(-3) S cm(-1) is obtained at LiI/HPN = 1: 4 (molar ratio) at room temperature. Comparison on the interactions of the Li+ ions with the hydroxyl and with the nitrile groups indicates that Li+-nitrile coordination is preferential. A light-to-electricity conversion efficiency of 1.8% at AM 1.5 illumination has been obtained on a DSSC employing this electrolyte. (C) 2004 The Electrochemical Society.