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V. O. Leonov, Ye. V. Shevchenko, E. G. Petrov
«Impact of Gate Potential on the Electroluminescence of the Molecular Photodiode»
PACS numbers: 05.60.Gg, 33.50.-j, 73.63.Nm, 78.60.Fi, 85.35.-p, 85.60.-q, 85.65.+h
In this work, we studied the mechanism of formation of the electroluminescence in a fluorophore molecule, which has an asymmetric distribution of electron density on the orbitals involved in electron transfer through the ‘electrode 1–molecule–electrode 2’ structure. The fluorophore is located in an electric field created by the voltage bias V and the gate potential \(V_G\). These potentials shift the position of the energy levels of the molecular orbitals of fluorophore molecule relative to the Fermi levels of metal electrodes and, thus, contribute to the appearance of resonant electron hopping between molecular orbitals and conducting states of the electrodes. Systems are analysed in detail, in which the lowest occupied and highest unfilled orbitals are the active molecular orbitals. As the centres of the electron densities of the orbitals are at various distances from the electrode surfaces, it leads to different electron hopping rates between the band states of the electrodes and the fluorophore orbitals. As a result, polarity arises in the formation of electroluminescence that manifests itself in the fact that the radiation powers of fluorophore at V > 0 and V < 0 are noticeably different. The critical values of the potentials corresponding to the switching-on and switching-off of electroluminescence are found, and the dependence of these potentials on both the position of the energy levels of the orbitals involved in the electron transmission and the gate potential is shown. As shown, at certain values of \(V_G\), electroluminescence is switched on at lower values of V. This can be used for controlling the electroluminescence in molecular optoelectronics.
Keywords: photon generation, fluorophore, gate potential, molecular electroluminescence, single-molecule device
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