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International Journal of Photoenergy
Volume 2014 (2014), Article ID 579476, 6 pages
http://dx.doi.org/10.1155/2014/579476
Research Article

J-Aggregates of Amphiphilic Cyanine Dyes for Dye-Sensitized Solar Cells: A Combination between Computational Chemistry and Experimental Device Physics

1Nano-Photochemistry and Solarchemistry Labs, Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo 11566, Egypt
2Center for Nanotechnology, School of Engineering and Applied Sciences, Nile University, Juhayna Square, Sheikh Zayed, 6th of October City, Giza 12588, Egypt
3Nano-Photochemistry Laboratory, Environmental Studies and Research Institute, University of Sadat City (USC), Sadat City 32879, Egypt
4Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo 11341, Egypt

Received 26 May 2014; Revised 13 July 2014; Accepted 21 July 2014; Published 26 August 2014

Academic Editor: Serap Gunes

Copyright © 2014 M. S. A. Abdel-Mottaleb et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report on the design and structure principles of 5,5′-6,6′-tetrachloro-1,1′-dioctyl-3,3′-bis-(3-carboxypropyl)-benzimidacarbocyanine (Dye 1). Such metal-free amphiphilic cyanine dyes have many applications in dye-sensitized solar cells. AFM surface topographic investigation of amphiphilic molecules of Dye 1 adsorbed on TiO2 anode reveals the ability of spontaneous self-organization into highly ordered aggregates of fiber-like structure. These aggregates are known to exhibit outstanding optical properties of J-aggregates, namely, efficient exciton coupling and fast exciton energy migration, which are essential for building up artificial light harvesting to the photovoltaic device. A light-to-electricity conversion efficiency of DSSC based on the metal free amphiphilic Dye 1 is , which is about 50% of that based on metal-based N719 Ru-dye (Di-tetrabutylammoniumcis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II)). DFT and TD-DFT studies show that large intramolecular charge transfer takes place from the HOMO to LUMO. HOMO is localized on a part of the molecule with almost no contribution from the carboxylic moiety. This clearly indicates that the anchoring carboxylic group plays a minor role.