Single-molecule LEDs from nanoscale electroluminescent junctions

Through pulsed operation, polarity is introduced in single Ag nanocluster (Ag₂-Ag₈) electroluminescence within seemingly nonpolar two-terminal nanoscale break junctions at room temperature. While observable with much higher power DC excitation, both high-frequency pulsed and AC operation lead to greatly increased spectrally and thermally stable electroluminescence with much narrower individual nanocluster electroluminescence spectra. Being polarity independent under both sinusoidal and DC excitations, pulsed electrical excitation of individual Ag nanoclusters has generated the first single-molecule LED by temporally separating hole and electron injection processes.