  The electroluminescence of a polythiophene wire suspended between two
metallic electrodes is probed using a scanning tunneling microscope. Under
positive sample voltage, the spectral and voltage dependencies of the emitted
light are consistent with the fluorescence of the wire junction mediated by
localized plasmons. This emission is strongly attenuated for the opposite
polarity. Both emission mechanism and polarity dependence are similar to what
occurs in organic light emitting diodes (OLED) but at the level of a single
molecular wire.
