Modification of Fluorescence Properties in Single Colloidal Quantum Dots by Coupling to Plasmonic Gap Modes

Efficient Auger relaxation in colloidal quantum dots (QDs) plays a crucial role in determining single-QD fluorescence behavior, for example, leading to fluorescence blinking and pure single-photon emission. Here, we demonstrate that when single-QD emission is coupled to a plasmonic gap mode, the fluorescence behavior is no longer dictated by nonradiative Auger relaxation, instead by radiative decay processes. In this case, annoying blinking can be largely suppressed accompanied by fluorescence enhancement. Moreover, the radiative decay rates for both exciton (X) and biexciton (BX) can be enhanced simultaneously owing to the broadband nature of a plasmonic gap mode with large Purcell effect. As a result, the BX quantum yields can be enhanced as high as that of single X emission which is derived from photon correlation measurement. This demonstration paves the way toward generating correlated photon pairs through BX-X cascade emission at room temperature based on cost-effective colloidal QDs.