Monolithic quasi-solid-state dye-sensitized solar cells based on iodine-free polymer gel electrolyte

A monolithic quasi-solid-state dye-sensitized solar cell assembled with an iodine-free polymer gel electrolyte (IFGE) and a printable mesoscopic carbon counter electrode was developed. The IFGE was prepared by employing an ionic liquid (1,2-dimethyl-3-propylimidazolium iodide, DMPII) as the charge transfer intermediate and a polymer composite as the gelator without the addition of iodine, exhibiting high conductivity and non-absorption characters. The dependences of ionic conductivity and photovoltaic performance on DMPII concentration in the IFGE were investigated. An overall power conversion efficiency (PCE) of 4.94% could be obtained for the IFGE with an ionic conductivity of 21.18 mS cm(-2) under 100 mW cm(-2) AM 1.5 illumination. The effects of additives lithium iodide (LiI) and N-methyl-benzimidazole (NMBI) on the photovoltaic performance of the devices were also investigated. An optimal efficiency of up to 6.97% was obtained and the results were substantiated by incident photon-to-current conversion efficiency (IPCE) spectrum, electrochemical impedance spectroscopy (EIS) and intensity modulated photovoltage spectroscopy (IMVS) measurements. (C) 2013 Elsevier B.V. All rights reserved.