Researchers from Tokyo's Institute of Science and Idemitsu Kosan recently reported a single‑particle photophysics study of colloidal BaZrS3 chalcogenide perovskite quantum dots (QDs), targeting them as a lead‑free, stable alternative to halide perovskites for light‑emitting applications. BaZrS3 offers a direct, visible‑range bandgap and robust chemical stability, and the key question here was how quantum confinement and surface defects govern its emission at the single‑QD level.
Structural and optical characterization. (a) Photo of BaZrS3 QD toluene suspension; (b) powder XRD data of BaZrS3 QDs (red) and BaZrS3 reference (blue); (c) TEM image of the synthesized BaZrS3 QDs; (d) size dispersion analyzed from the TEM images for 109 QDs; (e) high-resolution TEM image of a single QD showing the lattice fringes and d -spacing; (f ) absorption (blue) and PL (orange) spectra (normalized) of the BaZrS3 QD toluene suspension; (g – i) high-resolution XPS spectra for the Ba 3d (g), Zr 3d (h), and S 2p (i) core levels, fitted as described in the text. Image from: Nanoscale
The team synthesized colloidal BaZrS3 QDs by a hot‑injection method and obtained particles in the BaZrS3 crystal phase with a broad size distribution from 2 nm to 18 nm (average 7.6 nm). This broad size range spans strong to weak quantum‑confinement regimes and is reflected in ensemble optics: weak PL (solution PLQY ≈ 5%) with peaks at 491 nm and 504 nm plus a red shoulder, consistent with a mixture of sizes and local environments. Composition analysis showed nearly ideal Ba:Zr ≈ 1:1 but significant sulfur deficiency, pointing to abundant surface traps that can quench emission and currently limit device‑ready performance.
The study positions BaZrS3 QDs as a highly promising materials platform that combines a broadly size‑tunable bandgap, spectrally pure single‑particle emission and an addressable, surface‑trap‑driven blinking mechanism—key ingredients for next‑generation, lead‑free displays, LEDs and quantum light sources. The researchers are now looking to commercialize the technology, contact support@latticeventures.co for sample information and joint development opportunities.
Using wide‑field and confocal single‑particle PL microscopy on QDs dispersed in PMMA, the researchers observed clear PL blinking, where individual QDs switch between a bright ON state and a dim “grey” state, with ON‑time statistics strongly dependent on excitation power (21–647 W cm⁻²). Time‑resolved PL decays from single QDs are bi‑exponential, and crucially, fluorescence lifetime–intensity plots show that the average lifetime remains nearly constant as the intensity changes, identifying a B‑type blinking mechanism associated with population of a surface trap state above the conduction band. Ligand engineering to passivate these traps produces a substantial increase in PL intensity, demonstrating a clear handle to unlock much higher efficiencies through surface‑chemistry optimization.
Single‑QD spectra exhibit narrow linewidths with an average FWHM of 25.6 nm, while emission peak positions span a wide 468–646 nm range across the QD ensemble. This experimental distribution matches well with the theoretical transition energies predicted from the measured size distribution, providing direct evidence that the PL is governed by quantum confinement rather than dominant trap emission.
