Metallic Conductive Luminescent Film: Current Effect on Lifetime

We report an effect of electric current on luminescence lifetime without charge injection. To the best of our knowledge, this effect has not been reported before. To observe it, a metal-conductive luminescent film was fabricated, again for the first time. Specifically, nanoparticles of silica-coated CdS/CdSe quantum dots (SiQDs) were embedded in nests of continuous gold thin film, by a self-templating electroless process. The lifetime-current response is nearly linear, with a sensitivity of ~-0.17 nsec/mA over the range 0-700 mA. The effect is interpreted in terms of a local electric field component (and not the magnetic component) around each nested SiQD, and in terms of plasmon enhancement by electrical pumping, which allows coupling between the gold hot spots, namely the tips of the corrugated metal nests. Quenching of the luminescence of the QDs is diminished by the insulating silica layer, which still allows plasmonic coupling of SiQDs, as observed by luminescence life-time analysis and by surface enhanced Raman scattering (SERS). All of these phenomena require the special SiQD@Au embedding architecture, and are not observed with simple adsorption of SiQDs on continuous Au film.