Heralded Spectroscopy: a new single-particle probe for nanocrystal photophysics

Semiconductor nanocrystals feature multiply-excited states that display intriguing physics and significantly impact nanocrystal-based technologies. Fluorescence supplies a natural probe to investigate these states. Still, direct observation of multiexciton fluorescence has proved elusive to existing spectroscopy techniques. Heralded Spectroscopy is a new tool based on a breakthrough single-particle, single-photon, sub-nanosecond spectrometer that utilizes temporal photon correlations to isolate multiexciton emission. This proceedings paper introduces Heralded Spectroscopy and reviews some of the novel insights it uncovered into exciton-exciton interactions within single nanocrystals. These include weak exciton-exciton interactions and their correlation with quantum confinement, biexciton spectral diffusion, multiple biexciton species and biexciton emission polarization.