In this paper, we studied the influence of different cations on redox behavior of I- and I-3(-) by cyclic voltammetry and electrochemical impedance spectroscopy. It was demonstrated that increasing cation size tends to give rise to higher reductive activity of I- and lower diffusion coefficient of I-3(-) in these cations, alkylimidazolium, [Na subset of 15-C-5](+) and [K subset of 18-C-6](+). Moreover, we measured the performance of dye-sensitized solar cells (DSCs) with electrolyte containing [K subset of 18-c-6]I or 1,2-dimethyl-3-propylimidazolium iodide (DMPII). It was found that dye-sensitized solar cells (DSCs) with [K subset of 18-C-6]I give a little higher short-circuit photocurrent density and a little lower fill factor than DSCs with DMPII. (c) 2004 Elsevier Ltd. All rights reserved.