Plasmon-Enhanced Single-Molecule Electroluminescence: A Computational Study

Photoemission due to current formation through a molecular junction is studied theoretically. Placing a single molecule between two spherical leads in which plasmon excitations are in near-resonance to the molecular excitation energy, an increase in the emission intensity by more than three orders of magnitude is demonstrated. Such a plasmon-enhanced single-molecule electroluminescence can be obtained for a small as well as a large reorganization energy upon molecular excitation. In the latter case, a certain part of the vibrational progression in the emission spectrum undergoes an increase. For large charging energies of the molecule, electroluminescence enhancement can be observed in a voltage range around 2 V.