Publication date: 15th December 2025
The fluorescence spectra of individual semiconductor nanocrystals (NCs) can inform on key physical properties such as the emission pathway and dephasing mechanisms [1,2]. However, structural variations between individual particles broaden the ensemble fluorescence spectrum. This broadening obscures the single-NC lineshape and complicates efforts to understand key photo-physics [3]. Practically, understanding the degree of optical heterogeneity within a sample also benefits efforts to use NC materials in light-emitting diodes (LEDs) [4] and lasing [5].
Today, the standard technique for the determination of single-NC emission properties and optical heterogeneity is single-NC spectroscopy [1]. While powerful, this approach can suffer from user selection bias and low statistical significance. In addition, single-NC measurements typically require very photostable samples. To address these deficiencies, we introduce a novel photon-correlation technique that extracts single-NC emission spectra from a solution ensemble with high statistical rigor. Unlike other ensemble-level photon-correlation [6] or nonlinear techniques [7], our method is able to accurately resolve asymmetric spectra and identify sub-populations of emitters.
In this work, we first derive the theoretical connection between the measured intensity fluctuations and the single-NC spectrum. Next, we computationally model the experiment as a proof of concept. Then we construct the experimental optical setup and apply the measurement to a solution ensemble of red-emitting InP/ZnSe/ZnS NCs. Our measurement reveals a high degree of optical heterogeneity in the sample. Comparison of these results with other single-NC measurements provides experimental verification of our new technique. Finally, we use the new method to analyze a sample of lightly doped ZnSe1-xTex /ZnSe/ZnS NCs, a candidate material for blue quantum dot LEDs. We observe the presence of multiple spectral populations within the ZnSe1-xTex ensemble, which we attribute to separate distributions of excitonic and trapped emitters. Our results will inform future synthetic efforts to optimize ZnSe1-xTex NCs for commercial displays. More broadly, our results highlight the ability of the new technique to efficiently and accurately characterize samples of nanoscale emitters.
J.R.H., O.J.T., and S.T. acknowledge support from the Samsung Advanced Institute of Technology (SAIT). O.M.N. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Chemistry Program under award number DE-FG02-07ER46454. We gratefully acknowledge Dr. Gang Liu for building electronics used in the experimental optical setup.
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