Our research focuses on using single-particle photoluminescence (PL) spectroscopy to study the optical properties of Perovskite Nanocrystals (PNCs) and quantum shells (QSs) at the individual particle level. By leveraging advanced techniques such as confocal fluorescence microscopy and time-correlated single-photon counting (TCSPC), we explore fundamental photophysical processes, including single-photon emission, exciton dynamics, and blinking behavior. Our studies have revealed a transition from single- to multiphoton emission linked to thermally activated defect states, shedding light on how these materials behave as quantum light sources. (J. Phys. Chem. Lett. 2023, 14, 12, 2933–2939)
A key aspect of our work involves understanding and controlling blinking behavior, a phenomenon where nanocrystals switch between bright and dark states. We have demonstrated that ZnS capping layers and larger-core QS geometries can effectively suppress blinking by minimizing charged exciton populations and reducing non-radiative recombination pathways. Additionally, alumina encapsulation has proven to be an effective strategy for stabilizing emission by mitigating Auger recombination, ensuring prolonged and consistent light output from individual nanocrystals. (J. Am. Chem. Soc. 2023, 145, 24, 13326–13334 and ACS Materials Lett. 2023, 5, 5, 1411–1419)
(a) A low-resolution TEM image of PbS/CdS QDs and (b)a typical wide-field PL image of single QDs. (c) A representative PLintensity time trace of a single PbS/CdS QD.Figure 2. (a) Representative PL emission spectra of four single PbS/CdS QDs at 4 K. (b) Scatter plot of spectral line width Γ and peakenergy of single QDs. The top and the right panels display thedistribution histograms of peak energy and Γ, respectively.Nano Letters LetterDOI: 10.1021/acs.nanolett.9b02937Nano Lett. 2019, 19, 8519−85258520
Beyond fundamental studies, we apply single-photon counting and photon correlation spectroscopy to investigate emission dynamics and quantum efficiency at the single-particle level. By analyzing blinking traces, exciton lifetimes, and photon statistics, we aim to enhance the stability and performance of perovskite and quantum dot-based emitters. These insights contribute to the development of next-generation quantum optics, light-emitting devices, and nanoscale optoelectronics.