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Issue 26, 2010
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Electronic structure of large disc-type donors and acceptors

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Abstract

Searching for new π-conjugated charge-transfer systems, the electronic structure of a new acceptor–donor pair derived from coronene (C24H12) was investigated by ultraviolet photoelectron spectroscopy (UPS). The acceptor coronene-hexaone (C24H6O6, in the following abbreviated as COHON) and the donor hexamethoxycoronene (C30H24O6, abbreviated as HMC) were adsorbed as pure and mixed phases on gold substrates. At low coverage, COHON adsorption leads to the appearance of a charge-transfer induced interface state 1.75 eV below the Fermi energy. At multilayer coverage the photoemission intensity of the interface state drops and the valence spectrum of neutral COHON appears. The sample work function decreases from 5.3 eV (clean Au) to 4.8 eV (monolayer) followed by an increase to 5.6 eV (multilayer). The formation of a significant interface dipole due to charge-transfer at the metal–organic interface is possibly accompanied by a change in molecular orientation. HMC on Au exhibits no interface state and the sample work function decreases monotonically to ca. 4.8 eV (multilayer). The UPS spectra of individual donor and acceptor multilayers show good agreement with density functional theory modeling. In donor/acceptor mixed films the photoemission signal of the donor (acceptor) shifts to higher (lower) binding energy. This trend is predicted by the calculation and is anticipated when charge is transferred from donor to acceptor. We propose that mixed films of COHON and HMC constitute a weak charge-transfer system.

Graphical abstract: Electronic structure of large disc-type donors and acceptors

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Publication details

The article was received on 22 Dec 2009, accepted on 16 Mar 2010 and first published on 19 May 2010


Article type: Paper
DOI: 10.1039/B926999A
Citation: Phys. Chem. Chem. Phys., 2010,12, 7184-7193
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    Electronic structure of large disc-type donors and acceptors

    K. Medjanik, D. Kutnyakhov, S. A. Nepijko, G. Schönhense, S. Naghavi, V. Alijani, C. Felser, N. Koch, R. Rieger, M. Baumgarten and K. Müllen, Phys. Chem. Chem. Phys., 2010, 12, 7184
    DOI: 10.1039/B926999A

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