High-Throughput Characterization of Single-Quantum-Dot Emission Spectra and Spectral Diffusion by Multiparticle Spectroscopy

Abstract

In recent years, quantum dots (QDs) have emerged as bright, color-tunable light sources for various applications such as light-emitting devices, lasing, and bioimaging. One important next step to advance their applicability is to reduce particle-toparticle variations of the emission properties as well as fluctuations of a single QD's emission spectrum, also known as spectral diffusion (SD). Characterizing SD is typically inefficient as it requires time-consuming measurements at the single-particle level.Here, however, we demonstrate multiparticle spectroscopy (MPS) as a high-throughput method to acquire statistically relevant information about both fluctuations at the single-particle level and variations at the level of a synthesis batch. In MPS, we simultaneously measure emission spectra of many (20−100) QDs with a high time resolution. We obtain statistics on single-particle emission line broadening for a batch of traditional CdSebased core−shell QDs and a batch of the less toxic InP-based core−shell QDs. The CdSe-based QDs show significantly narrower homogeneous line widths, less SD, and less inhomogeneous broadening than the InP-based QDs. The time scales of SD are longer in the InP-based QDs than in the CdSe-based QDs. Based on the distributions and correlations in single-particle properties, we discuss the possible origins of line-width broadening of the two types of QDs. Our experiments pave the way to large-scale, high-throughput characterization of single-QD emission properties and will ultimately contribute to facilitating rational design of future QD structures.

Size-Dependent Optical Properties of InP Colloidal Quantum Dots

“…The relatively narrow single-QD line widths of 60–80 meV and much broader ensemble line widths (200 meV) are consistent with previous studies on InP-based core/shell QDs . Recent work has confirmed that InP-based core/shell QDs can have narrow single-QDs line widths but also showed that they on average suffer more from spectral diffusion (Figure S8b) and that inhomogeneous broadening is more significant than for CdSe-based QDs . Our measurements in Figure b show narrow single-QD line widths even for core-only InP QDs.…”

“…29 Recent work has confirmed that InP-based core/shell QDs can have narrow single-QDs line widths but also showed that they on average suffer more from spectral diffusion (Figure S8b) and that inhomogeneous broadening is more significant than for CdSe-based QDs. 30 Our measurements in Figure 3b show narrow single-QD line widths even for coreonly InP QDs. This is encouraging, as it promises the possibility of narrower line widths in InP CQDs with improved surface passivation or engineered electron−phonon coupling.…”