Dye-Sensitized Solar Cells Based on a Natural Low Cost Halochromic Sensitizer
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Dye-Sensitized Solar Cells Based on a Natural Low Cost Halochromic Sensitizer Michael I. Ibrahim1,2, Maria J. Bassil1, Umit B. Demirci2, Georges El Haj Moussa1, Mario R. El Tahchi1 and Philippe Miele2 1
LPA-GBMI, Department of Physics, Lebanese University - Faculty of Sciences II, PO Box 90656 Jdeidet, Lebanon, email: [email protected], Tel: +961 3 209688, Fax: +961 1 681553. 2 Université Lyon 1, CNRS, UMR 5615, Laboratoire des Multimatériaux et Interfaces, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne, France, email: [email protected].
ABSTRACT Since their re-introduction as new generation solar cells in 1991, dye-sensitized solar cells (DSSCs) have been studied extensively to improve their efficiency and their stability. Few papers have reported the usage of natural dyes in the fabrication of DSSCs. We are most interested in these dyes being easy to extract, low cost and with tunable absorption. For example, Anthocyanin is extracted from red cabbage and is present in a multitude of colors ranging from red to yellow to violet according to the pH. In this study, two industrial types of titanium dioxide powders, the Degussa P 25 and the Crystal 128 with different particle sizes 21 and 200 nm respectively, were used to prepare DSSCs. The dye used is anthocyanin and its color is varied by varying the pH of the medium. The pH effect on the light absorption of anthocyanin in the visible range and the optical properties of titanium dioxide dyed with anthocyanin and coumarin 102 are investigated using UV-Vis spectroscopy. The open-circuit voltage of all the samples is tested and it if found out that it is dependant on the dye color. INTRODUCTION In 1991, M. Grätzel re-introduced the photoelectrochemical effect in dye-sensitized solar cells (DSSCs) [1]. Three components are essential for the functioning of a DSSC: a titanium dioxide layer (TiO2), a charge transfer dye used to sensitize the TiO2 film and to enhance its absorption in the visible range and an electrolyte containing I-/I3- redox couple which restores the original state of the dye by electron donation [2]. TiO2 is an n-type semiconductor used in various applications for its high chemical stability, high photocatalytic activity, low cost and non-toxicity. The search for a stable, low cost and efficient dye has led to the synthesis of a wide variety of sensitizers with different absorption coefficient and high efficiencies. The majority of the sensitizers are based on ruthenium where efficiency as high as 11.1% was recorded with black dye [3]. Large-area (27 cm2) DSSC based on black dye with a module-efficiency of 8.4% was produced. The insertion of Li ions into ruthenium dye leads to a more thermally stable DCCS [4]. Other dyes such as cyanine dye with and without benzothiadiazole have been used by Tian et al. for the preparation of DSSCs with a recorded efficiency of 7.62% and 6.58% respectively [5]. Different novel coumarin dyes with variable absorption wavelengths have been synthesized for the fabrication of DSSC with a maximum efficiency of 5
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