Zipping Up and Down

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Science  28 May 2010:
Vol. 328, Issue 5982, pp. 1077-1079
DOI: 10.1126/science.328.5982.1077-d
CREDIT: N. SAKAI ET AL., J. AM. CHEM. SOC. 132, 10.1021/JA101944R (2010)

In general, the first step in deriving electricity from sunlight is to liberate bound charges for current flow. Once such charges are generated in a photovoltaic system, the next challenge is to insure that the carriers separate and travel all the way to electrodes for collection, rather than unproductively recombining in place. Sakai et al. report the stepwise assembly of units consisting of naphthalenediimide chromophores (tuned in gap energy to create an electron transport gradient) attached to either p-oligophenyl hole donors or p-oligophenylethynyl hole acceptors. Sequential zipper assembly created stacks of several of these types of units on a gold substrate. Under irradiation with simulated solar emission, the photocurrents reached saturation at about 50 layers, indicating that long-distance carrier transport was achieved in this supramolecular construct.

J. Am. Chem. Soc. 132, 10.1021/ja101944r (2010).

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