Materials Science

Dimeric Dopants

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Science  23 Dec 2011:
Vol. 334, Issue 6063, pp. 1605
DOI: 10.1126/science.334.6063.1605-c

Just as with inorganic semiconductors, dopants can improve the conductivity of organic electronic materials. Alkali metals have been used as electron-donating (n-type) dopants, but they can diffuse through the material and can create charge trapping sites. Strongly reducing molecular n-dopants are attractive alternatives but are generally too air-sensitive for practical use. Guo et al. show that the dimeric forms of cyclopentadienyl-type sandwich compounds, such as the dimeric form of rhodocene and (pentamethylcyclopentadienyl)ruthenium(1,3,5-trialkylbenzene) (where alkyl can be methyl or ethyl), are moderately air-stable in the solid state. With solid-state electron affinities as low as 2.8 eV, these compounds can be used to n-dope a variety of electron-transport materials both in solution and in the vapor phase. The rhodocene dimer was used as the n-dopant for copper phthalocyanine in a p-i-n homojunction diode that achieved a rectification ratio of greater than 106 at a bias of 4 V.

Adv. Mater. 10.1002/adma.201103238 (2011).

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