Colloidal quantum dots (QDs) offer high color purity essential to high-quality liquid crystal displays (LCDs), which enables unprecedented levels of color enrichment in LCD-TVs today. However, for LCDs requiring polarized backplane illumination in operation, highly polarized light generation using inherently isotropic QDs remains a fundamental challenge. Here, we show strongly polarized color conversion of isotropic QDs coupled to Fano resonances of v-grooved surfaces compatible with surface-normal LED illumination for next-generation QD-TVs.
View Article and Find Full Text PDFWe investigate the fundamental optical properties of single zinc-blende InP/ZnSe/ZnS nanocrystals (NCs) using frequency- and time-resolved magneto-photoluminescence spectroscopy. At liquid helium temperature, highly resolved spectral fingerprints are obtained and identified as the recombination lines of the three lowest states of the band-edge exciton fine structure. The evolutions of the photoluminescence spectra and decays under magnetic fields show evidence for a ground dark exciton level 0 with zero angular momentum projection along the NC main elongation axis.
View Article and Find Full Text PDFQuantum dot light-emitting diodes (QD-LEDs) are one of the most promising self-emissive displays in terms of light-emitting efficiency, wavelength tunability, and cost. Future applications using QD-LEDs can cover a range from a wide color gamut and large panel displays to augmented/virtual reality displays, wearable/flexible displays, automotive displays, and transparent displays, which demand extreme performance in terms of contrast ratio, viewing angle, response time, and power consumption. The efficiency and lifetime have been improved by tailoring the QD structures and optimizing the charge balance in charge transport layers, resulting in theoretical efficiency for unit devices.
View Article and Find Full Text PDFInP quantum dots (QDs) are the material of choice for QD display applications and have been used as active layers in QD light-emitting diodes (QDLEDs) with high efficiency and color purity. Optimizing the color purity of QDs requires understanding mechanisms of spectral broadening. While ensemble-level broadening can be minimized by synthetic tuning to yield monodisperse QD sizes, single QD line widths are broadened by exciton-phonon scattering and fine-structure splitting.
View Article and Find Full Text PDFObjective: The objective of the study was to assess in vivo the validity of a new imaging device in quantifying the scarring process over time and to compare its data with the expertise of dermatologist and patients' self-appraisals.
Materials And Methods: A total of 37 Korean women, aged 20-50 year, with closed scars of different types, were enrolled after a dermatological evaluation. All subjects applied daily a hydrating cream on their scars for 2 months.
Isotropic InP/ZnSe/ZnS quantum dots (QDs) are prepared at a high reaction temperature, which facilitates ZnSe shell growth on random facets of the InP core. Fast crystal growth enables stacking faults elimination, which induces anisotropic growth, and as a result, improves the photoluminescence (PL) quantum yield by nearly 20%. Herein, the effect of the QD morphology on photophysical properties is investigated by observing the PL blinking and ultrafast charge carrier dynamics.
View Article and Find Full Text PDFUpon demonstrating self-luminescing quantum dot based light-emitting devices (QD-LEDs), rapid Auger recombination acts as one of the performance limiting factors. Here, we report the Auger processes of highly luminescent InP/ZnSe/ZnS QDs with different midshell structures that affect the performances of QD-LEDs. Transient PL measurements reveal that exciton-exciton binding energy is dependent on the midshell thickness, which implies that the intercarrier Coulomb interaction caused by the introduction of excess charges may come under the influence of midshell thickness which is in contrast with the nearly stationary single exciton behavior.
View Article and Find Full Text PDFIncreasing the quantum yields of InP quantum dots is important for their applications, particularly for use in consumer displays. While several methods exist to improve quantum yield, the addition of inorganic metal halide salts has proven promising. To further investigate this phenomenon, InP quantum dots dispersed in tetrahydrofuran were titrated with ZnCl, ZnBr, and InCl.
View Article and Find Full Text PDFThe visualization of accurate colour information using quantum dots has been explored for decades, and commercial products employing environmentally friendly materials are currently available as backlights. However, next-generation electroluminescent displays based on quantum dots require the development of an efficient and stable cadmium-free blue-light-emitting device, which has remained a challenge because of the inferior photophysical properties of blue-light-emitting materials. Here we present the synthesis of ZnSe-based blue-light-emitting quantum dots with a quantum yield of unity.
View Article and Find Full Text PDFSemiconductor quantum dots (QDs) are spotlighted as a key type of emissive material for the next generation of light-emitting diodes (LEDs). This work presents the investigation of the electrochemical charging effect on the absorption and emission of the InP/ZnSe/ZnS QDs with different mid-shell thicknesses. The excitonic peak is gradually bleached during electrochemical charging, which is caused by 1S (or 1S ) state filling when the electron (or hole) is injected into the InP core.
View Article and Find Full Text PDFThe emission linewidth of a semiconducting nanocrystal (NC) significantly affects its performance in light-emitting applications, but its fundamental limit is still elusive. Herein, we analyze the exciton-phonon coupling (EPC) from Huang-Rhys (HR) factors using ab initio calculations and compute emission line shapes of CdSe NCs. When surface traps are absent, acoustic modes are found to dominate EPC.
View Article and Find Full Text PDFWe investigated the dependence of the spectral diffusion and blinking behaviors of indium phosphide (InP) based core/shell/shell quantum dots (QDs) on their mid-shell compositions. We synthesized two types of core/shell/shell QDs having different mid-shell structures by controlling the shell thickness, the total sizes, and the selenium to sulfur ratios. The QDs with a discrete mid-shell (DS-QDs) exhibited a higher photoluminescence (PL) quantum yield (QY) and a narrower PL linewidth than the QDs with a gradient mid-shell (GS-QDs).
View Article and Find Full Text PDFQuantum dot (QD) light-emitting diodes (LEDs) are ideal for large-panel displays because of their excellent efficiency, colour purity, reliability and cost-effective fabrication. Intensive efforts have produced red-, green- and blue-emitting QD-LEDs with efficiencies of 20.5 per cent, 21.
View Article and Find Full Text PDFTreatment of InP colloidal quantum dots (QDs) with hydrofluoric acid (HF) has been an effective method to improve their photoluminescence quantum yield (PLQY) without growing a shell. Previous work has shown that this can occur through the dissolution of the fluorinated phosphorus and subsequent passivation of indium on the reconstructed surface by excess ligands. In this article, we demonstrate that very significant luminescence enhancements occur at lower HF exposure though a different mechanism.
View Article and Find Full Text PDF[This corrects the article on p. 373 in vol. 68, PMID: 26257850.
View Article and Find Full Text PDFBackground: This study was performed to compare the incidence of emergence agitation (EA) between inhalation and intravenous anesthesia induction in children after sevoflurane anesthesia.
Methods: In this prospective and double-blind study, 100 children aged 3 to 7 years were enrolled. Subjects were randomly assigned to the sevoflurane (Group S) or thiopental (Group T) anesthesia induction groups.
Korean J Anesthesiol
December 2014
Theoretical calculations based on density functional theory were performed to provide better understanding of the size dependent electronic properties of InP quantum dots (QDs). Using a hybrid functional approach, we suggest a reliable analytical equation to describe the change of energy band gap as a function of size. Synthesizing colloidal InP QDs with 2-4 nm diameter and measuring their optical properties was also carried out.
View Article and Find Full Text PDFA highly luminescent and photostable quantum dot-silica monolith (QD-SM) substance was prepared by preliminary surface exchange of the QDs and base-catalyzed sol-gel condensation of silica. The SM was heavily doped with 6-mercaptohexanol exchanged QDs up to 12 vol % (26 wt %) without particle aggregation. Propylamine catalyst was important in maintaining the original luminescence of the QDs in the SM during sol-gel condensation.
View Article and Find Full Text PDFColor conversion: a quantum dot (QD) structure consisting of an alloy core (CdSe//ZnS) and multishells (CdSZnS) was prepared. The photoluminescence of the QDs could be tuned especially in the green-light region by controlling the thickness of the inner CdS shell. The alloy core/multishell (AC/MS) QDs showed a quantum efficiency of 100 % and a narrow spectrum width.
View Article and Find Full Text PDFJ Nanosci Nanotechnol
December 2007
Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates.
View Article and Find Full Text PDFThe shape of silver sulfide nanomaterials was successfully controlled by understanding the origin of the mixed-shape problem.
View Article and Find Full Text PDFWe demonstrate the ability to use a photolithographic method to make patterned nanocrystal film for device applications. Exposing a nanocrystal film to strong UV light allowed the oleic acid ligands on the surface of the nanocrystals to form an insoluble cross-linked network while the unexposed areas were still soluble to toluene solvent. Therefore, the UV light exposure through a shadow mask followed by solvent rinsing produced a small feature size on the order of 2 mum.
View Article and Find Full Text PDF