Colloidal lead halide perovskite quantum dots, due to their optical versatility and facile solution processability, have been recently recognized as components of various optoelectronic devices. Detailed understanding of their exciton recombination dynamics at the single-particle level is necessary for utilizing their full potential. We conducted spectroscopic studies of the excitons and biexciton dynamics in single CsPbBr 3 perovskite quantum dots. It was found that while the rates of radiative recombination remain essentially constant, the overall relaxation process is dominated by nonradiative recombination of single excitons and biexcitons. The radiative lifetime scaling is determined to be ∼1.0 for single exciton and ∼4.4 for biexcitons. A linear dependence of fluorescence lifetime vs intensity distribution agrees well with the prediction of the model of multiple recombination centers. The blinking mechanism of CsPbBr 3 quantum dots is addressed by considering the trion states under higher excitation powers.

Anisotropy in crystals arises from different lattice periodicity along different crystallographic directions, and is usually more pronounced in two dimensional (2D) materials. Indeed, in the emerging 2D materials, electrical anisotropy has been one of the recent research focuses. However, key understandings of the in-plane anisotropic resistance in low-symmetry 2D materials, as well as demonstrations of model devices taking advantage of it, have proven difficult. Here, we show that, in few-layered semiconducting GaTe, electrical conductivity anisotropy between x and y directions of the 2D crystal can be gate tuned from several fold to over 10 3 . This effect is further demonstrated to yield an anisotropic non-volatile memory behavior in ultra-thin GaTe, when equipped with an architecture of van der Waals floating gate. Our findings of gate-tunable giant anisotropic resistance effect pave the way for potential applications in nanoelectronics such as multifunctional directional memories in the 2D limit.

Monolayer molybdenum disulfide (MoS2), a direct bandgap semiconductor with atomic thickness, provides significant advantages in many applications including high‐performance electronics, light emitters, and photodetectors/sensors. Controlling the electronic and optical properties of atomic‐layered MoS2 is extremely important for its practical applications. Interestingly, modulating the optical properties by physical routes, such as layer thickness, twist angle, tensile strain, temperature, gas physisorption and electrical doping, is more attractive, as these methods can control optical properties in real‐time, reversible, and in situ. The physical routes would be beneficial for understanding the fundamentals of electronic and optical properties of atomic‐layered MoS2, and also for its promising application in advanced optical materials and next‐generation electronic devices. This review highlights recent, state‐of‐the‐art research on tuning the optical properties of atomic‐layered MoS2 (including monolayer and few‐layer MoS2). Physical routes and proposed mechanisms of these modulations are discussed. Crystal structures and electronic band properties of atomic‐layered MoS2 are also reviewed, as they play important roles in understanding the modulation mechanisms. Finally, potential optical applications in electronic and optoelectronic devices based on tunable optical features are described, and a future prospective in this exciting field is presented.

In fluorescence imaging and detection, undesired fluorescence interference (such as autofluorescence) often hampers the contrast of the image and even prevents the identification of structures of interest. Here, we develop a quantum coherent modulationenhanced (QCME) single-molecule imaging microscopy (SMIM) to substantially eliminate the strong fluorescence interference, based on manipulation of the excitedstate population probability of a single molecule. By periodically modulating the phase difference between the ultrashort pulse pairs and performing a discrete Fourier transform of the arrival time of emitted photons, the decimation of single molecules from strong interference in QCME-SMIM has been clearly determined, where the signal-tointerference ratio is enhanced by more than 2 orders of magnitude. This technique, confirmed to be universal to organic dyes and linked with biomacromolecules, paves the way to high-contrast bioimaging under unfavorable conditions.

N-type semiconductor indium tin oxide (ITO) nanoparticles are used to effectively suppress the fluorescence blinking of single near-infrared-emitting CdSeTe/ZnS core/shell quantum dots (QDs), where the ITO could block the electron transfer from excited QDs to trap states and facilitate more rapid regeneration of neutral QDs by back electron transfer. The average blinking rate of QDs is significantly reduced by more than an order of magnitude and the largest proportion of on-state is 98%, while the lifetime is not considerably reduced. Furthermore, an external electron transfer model is proposed to analyze the possible effect of radiative, nonradiative, and electron transfer pathways on fluorescence blinking. Theoretical analysis based on the model combined with measured results gives a quantitative insight into the blinking mechanism.

Solid-state quantum emitters play a critical role in the application of quantum information technology. Quantum emitters with high brightness at room temperature can be realized in hBN, and it has become a current research hotspot. However, much of the research up to now only produced quantum emitters at the edges and wrinkles of hBN, which tremendously limited the usage of the quantum emitters. In this work, heavy ions irradiation methods were employed to produce highquality quantum emitters in the middle region of the hBN sample. The quantum emitter production engineering via heavy ions irradiation was systematically investigated. The dependence of irradiated ion type, energy, and fluence, as well as the thickness of the hBN flakes, on the production efficiency of the hBN quantum emitters were analyzed in detail. The characteristics of luminescence of quantum emitters, such as second-order correlation function g (2) (τ), stability, polarization, and saturation, were all compared with different irradiation conditions. In addition, based on the wavelength statistical results of quantum emitters in hBN, the transition energies of various intrinsic point defects in hBN were studied through first-principles calculations to reveal the originations of luminescence. The calculation results indicated that the V N , V B , and B i point defects were possible candidates of the quantum emitter centers. Overall, in this study, according to experimental characterizations, heavy ion irradiation should be an efficient method to produce stable, ultrabright, highly linearly polarized quantum emitters in hBN flakes.

Intrinsic photobleaching and photoluminescence (PL) intermittency of single quantum dots (QDs), originating from photo-oxidation and photo-ionization respectively, are roadblocks for most single-dot applications. Here, we effectively suppress the photobleaching and the PL intermittency of single near-infrared emitting QDs with p-phenylenediamine (PPD). The PPD cannot only be used as a high-efficient reducing agent to remove reactive oxygen species around QDs to suppress the photo-oxidation, but can also bond with the surface defect sites of single QDs to reduce electron trap states to suppress the photo-ionization. It is shown that the survival time of single QDs, the on-state probability of PL intensity traces, and the total number of emitted photons are significantly increased for single QDs in PPD compared with that on glass coverslip.

Lead halide perovskite quantum dots (QDs) are promising materials for next‐generation photoelectric devices because of their low preparation costs and excellent optoelectronic properties. In this study, the blinking mechanisms and the intrinsic quantum‐confined Stark effect (IQCSE) in single organic–inorganic hybrid CH3NH3PbBr3 perovskite QDs using single‐dot photoluminescence (PL) spectroscopy is investigated. The PL quantum yield‐recombination rates distribution map allows the identification of different PL blinking mechanisms and their respective contributions to the PL emission behavior. A strong correlation between the excitation power and the blinking mechanisms is reported. Most single QDs exhibit band‐edge carrier blinking under a low excitation photon fluence. While under a high excitation photon fluence, different proportions of Auger‐blinking emerge in their PL intensity trajectories. In particular, significant IQCSEs in the QDs that exhibit more pronounced Auger‐blinking are observed. Based on these findings, an Auger‐induced IQCSE model to explain the observed IQCSE phenomena is observed.