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Quantum‐Chemical Characterization of the Origin of Dipole Formation at Molecular Organic/Organic Interfaces
Author(s) -
Avilov Igor,
Geskin Victor,
Cornil Jérôme
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200800632
Subject(s) - dipole , acceptor , chemical physics , materials science , tetrathiafulvalene , molecule , charge (physics) , polarization (electrochemistry) , electron , electron acceptor , ionization energy , electron transfer , ionization , atomic physics , photochemistry , condensed matter physics , chemistry , physics , organic chemistry , ion , quantum mechanics
Recent experiments have reported a vacuum level shift at the interface between organic materials due to the formation of an interface dipole layer. On the basis of quantum‐chemical calculations, this paper sheds light on the factors contributing to the formation of an interface dipole between an electron donor and an electron acceptor, considering as model system a complex made of tetrathiafulvalene (TTF) as a donor and tetracyanoquinodimethane (TCNQ) as an acceptor. The results indicate that the interface dipole is governed both by charge‐transfer and polarization effects and allow for disentangling of their respective contributions. Two regimes of charge transfer can be distinguished depending on the strength of the electronic coupling: a fractional charge transfer occurs in the strong coupling regime while only integer charges are transferred when the coupling is weak. The polarization contribution can be significant, even in the presence of a pronounced charge transfer between the donor and acceptor molecules. The values of ionization potential and electron affinity of the donor and acceptor molecules may experience shifts as large as several tenths of an eV at the interface with respect to the isolated compounds.