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Atomic Level Resolution of Dye Regeneration in the Dye-Sensitized Solar Cell

TitleAtomic Level Resolution of Dye Regeneration in the Dye-Sensitized Solar Cell
Publication TypeJournal Article
Year of Publication2013
AuthorsRobson, KCD, Hu, K, Meyer, GJ, Berlinguette, CP
JournalJOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume135
Pagination1961-1971
Date PublishedFEB 6
ISSN0002-7863
Abstract

Two donor-acceptor organic dyes have been synthesized that differ only by a two-heteroatom change from oxygen to sulfur within the donor unit. The two dyes, (E)-3-(5-(4-(bis(4-(hexyloxy)phenyl)amino)phenyl)thiophen-2-yl)-2-cyanop rop-2-enoic acid (Dye-O) and (E)-3-(5-(4-(bis(4-(hexylthio)phenyl)amino)phenyl)thiophen-2-yl)-2-cyano prop-2-enoic acid) (Dye-S), were tested in solar cell devices employing both I-3(-)/I–based and {[}Co(bpy)(3)](3+/2+) redox mediators. Power conversion efficiencies over 6% under simulated AM 1.5 illumination (1 Sun) were achieved in both electrolytes. Despite similar optical and redox properties for the two dyes, a consistently higher open-circuit voltage (V-oc) was measured for Dye-S relative to Dye-O. The improved efficiency observed with Dye-S in an iodide redox mediator is against the commonly held view that sulfur atoms promote charge recombination attributed to inner-sphere interactions. Detailed mechanistic studies revealed that this is a consequence of a 25-fold enhancement of the regeneration rate constant that enhances the regeneration yield under open circuit conditions. The data show that a high short circuit photocurrent does not imply optimal regeneration efficiency as is often assumed.

DOI10.1021/ja311640f