Plasmon-Enhanced Photoemission from a Single Y3N@C80 Fullerene

Rare earth ions are the backbone of a wide range of optoelectronic applications, ranging from solid-state lasers and fiber amplifiers to silicon photonics. So far experiments on single rare-earth ions have been elusive because of the long excited state lifetimes and low absorption cross sections. Here we present the first single molecule photoemission study of an endohedral metallofullerene (Y3N@C-80). This molecule has a low intrinsic photoluminescence quantum yield and a long radiative lifetime. We find that the Y3N species is rigidly attached to the C-80 cage, imparting a fixed absorption dipole moment to the molecule as a whole. To improve the absorption and emission of light, we couple single Y3N@C-80 molecules to single gold nanoparticles, which results in a photoluminescence enhancement of 2 orders of magnitude. Such unexpectedly high enhancements are a consequence of the low intrinsic quantum yield of Y3N@C-80. Our work paves the way for applications of rare-earth ions on the single emitter level.