PHYS 719 |
| This talk reviews recent progress in molecular doping of organic semiconductors, which is poised to become an important tool to increase film conductivity, control Fermi level position and facilitate carrier injection in organic devices. P-type doping of common hole-transport materials is achieved with molecules like the electronegative fluorinated F4-TCNQ. Energetics of doping are determined by electron spectroscopy. High film conductivity and injection enhancement by carrier tunneling through a narrow depletion region are demonstrated. N-doping is more challenging, because of the low electron affinity (~1.5-2.5 eV) of most molecular materials of interest. N-dopants must have very low ionization energy and are thus inherently instable against oxidation. We report on the use of the strongly reducing and volatile molecule bis(cyclopentadienyl)-cobalt(II) (cobaltocene, CoCp2) (IE<4.0 eV) and derivatives, such as decamethyl CoCp2 to n-dope materials like phthalocyanines and pentacene. Current work on the doping of Alq3 and other electron transport materials will be discussed. |
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Emergence of Function in Molecular Assemblies
1:20 PM-4:50 PM, Thursday, August 23, 2007 BCEC -- 157B, Oral
Division of Physical Chemistry |