Deactivating charged states in colloidal quantum dots by Förster resonance energy transfer

Colloidal quantum dots (QDs) possess size/shape/surface-tunable optical and electronic properties, making them promising building blocks for optoelectronic applications. However, the fluorescence intermittency, also known as “blinking,” observed in individual QDs is a pervasive phenomenon. The dark state (trion state) in blinking experiences non-radiative recombination processes, such as trap-mediated recombination and Auger–Meitner recombination, which significantly diminish the quantum efficiency of the QDs. Despite efforts to mitigate blinking phenomena through chemical engineering of QDs structures and their environments, blinking continues to impede the application of single QDs, particularly in single photon sources. This study demonstrates that Förster resonance energy transfer (FRET) from green QDs (donor) to individual red QDs (acceptor) can effectively suppress fluorescence intermittency. The findings indicate that FRET facilitates the removal of excess charges from the charged state (dark state, trion state), allowing the QDs to transition from the lower quantum yield trion state to the higher quantum yield single-exciton state (bright state). Our research confirms that FRET can inhibit fluorescence intermittency by deactivating the charged state.