%0 Journal Article
%T Highly Conductive Redox-Couple Solid Polymer Electrolyte System: Blend-KI-I2 for Dye-Sensitized Solar Cells
%A Ravindra Kumar Gupta
%A Hee-Woo Rhee
%J Advances in OptoElectronics
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/102932
%X Ionic conductivity of a redox-couple solid polymer electrolyte system, ( ) blend: [0.9KIˋ:ˋ0.1I2] with in weight fraction, is reported. A blend of poly(ethylene oxide) (abbreviated as PEO) and succinonitrile in equal weight fraction was used as a polymeric matrix instead of the PEO and succinonitrile because of its low-cost, electrical conductivity superior to the PEO, and thermal stability better than the succinonitrile. The electrolyte with showed ionic conductivity of Sˋcmˋ1 and iodine ion diffusivity of nearly ˋcm2ˋsˋ1 at 25∼C. The conductivity and diffusivity values were nearly two orders of magnitude higher than those of the PEO-KI-I2 due to the improved PEO crystallinity. It also exhibited dye-sensitized solar cell efficiency of 2.2% at 100ˋmWˋcmˋ2, which is twice of the cell prepared using the PEO-KI-I2 only. 1. Introduction Following the invention of low-cost dye-sensitized solar cells (DSSCs), redox-couple solid polymer electrolytes have attracted considerable attention in recent years [1, 2]. These electrolytes eliminate the shortcomings of the liquid/gel electrolytes, such as leakage/evaporation of organic solvent especially at elevated temperatures, electrode corrosion, a need of hermetic sealing, and scale up of the manufacturing process. The PEO-MI-I2 (M = Li, Na, or K) electrolyte-based DSSCs exhibited energy conversion efficiency ( ) of 0.01每2% under the irradiation of 100ˋmWˋcmˋ2 [2每6]. It was attributed to low ionic conductivity ( ~ 10ˋ6每10ˋ5ˋSˋcmˋ1) of electrolytes and poor interfacial contacts between the electrolyte, TiO2, and dye at nanopores. The blending of PEO with a low molecular weight ether-based polymer improved the ionic conductivity, interfacial contacts, and, thus, the cell performance [3, 6, 7]. Dispersion of inorganic nanofiller into the electrolyte enhanced conductivity via providing the highly conductive space-charge regions and improved cell efficiency via penetration into the TiO2 nanopores [6, 8]. Recently, DSSCs with succinonitrile-ionic liquid-based electrolytes have showed relatively high efficiency, 5每6.7% at 25∼C due to high ionic conductivity (10ˋ4每10ˋ3ˋSˋcmˋ1), and iodine ion diffusivity (~10ˋ6ˋcm2ˋsˋ1) of electrolytes along with better interfacial contacts [9, 10]. The succinonitrile (abbreviated as SN) acts as a solvent because of its low melting temperature ( , ~54∼C) and high dielectric constant (~55). It also provides vacancies for ion transport in its plastic crystal phase between ˋ35∼C and 54∼C. However, low -value (~40∼C) and high-temperature instability of the electrolytes limited the use of the
%U http://www.hindawi.com/journals/aoe/2011/102932/