Fabrication and characterization of red-emitting electroluminescent devices based on thiol-stabilized semiconductor nanocrystals

Thiol-capped CdTe nanocrystals were used to fabricate light-emitting diodes, consisting of an emissive nanocrystal multilayer deposited via layer-by-layer, sandwiched between indium-tin-oxide and aluminum electrodes. The emissive and electrical properties of devices with different numbers of nanocrystal layers were studied. The improved structural homogeneity of the nanocrystal multilayer allowed for stable and repeatable current- and electroluminescence-voltage characteristics. These indicate that both current and electroluminescence are electric-field dependent. Devices were operated under ambient conditions and a clear red-light was detected. The best-performing device shows a peak external efficiency of 0.51% and was measured at 0.35mA/cm2 and 3.3V

Cathodic and Anodic Material Diffusion in Polymer/Semiconductor-Nanocrystal Composite Devices

In the present day, the information technologies and telecommunications sector continually increase their demand for low cost, low power consumption, high performance electroluminescent devices for display applications. Furthermore, general lighting applications, such as white light and large array colour displays, would also benefit from an increase in the overall efficiency. Several technologies are being investigated to fulfill these needs, such as organic light emitting diodes (OLED), polymeric light emitting diodes (PLED) and field effect emission devices. A new and promising technology is light emitting devices (LEDs) based on nanostructured materials. With organic LEDs (OLEDs) already making an impact on the market in an increasingly large number of applications, hybrid technologies based on organic/inorganic nano-composites are a potential the next step. The incorporation of highefficiency fluorescent semiconductor nanoparticles has been shown to have a beneficial effect on device performance, [1] modify the colour output from the device 2 and provide a simplified route to generation of LED type devices. [3

Tetrazoles: Synthesis, Structures, Physico-Chemical Properties and Application

The paper represents a brief review of works published by the authors over a period of 1980-2003 years in the field of synthesis and investigations of properties of tetrazole derivatives. The main attention is given to problems of regioselective functionalization of the tetrazole ring and the development of simple and convenient methods for the synthesis of N- and C-substituted tetrazoles, to peculiarities of structure of crystalline tetrazoles including quaternary salts and complexes with transition metal salts as well as to the data on electronic, spatial structure and energetic characteristics of tetrazoles obtained using both quantum-chemical methods and IR-, XH , 13C and 15N NMR spectroscopy. The features of thermal decomposition and combustion of various tetrazoles and polyvinyltetrazoles determining the prospects of their use as effective components of different kind combustible and thermally decomposing systems, including those capable of liquid-flame combustion, which has been revealed for the first time, are considere

3-Phenyl-2-(1H-tetra­zol-1-yl)propanoic acid monohydrate

In the title compound, C10H10N4O2·H2O, the dihedral angle between the tetra­zole and benzene rings is 63.24 (11)°. The crystal structure is stabilized by intra­molecular O—H⋯N and O—H⋯O hydrogen bonds

Selectively Tunable Luminescence of Perovskite Nanocrystals Embedded in Polymer Matrix Allows Direct Laser Patterning

Cesium lead halide perovskite nanocrystals (NCs) have gained enormous attention as promising light-emitting and light-converting materials. Most of their applications require embedding NCs in various matrices, which is a challenging task due to their low stability, especially in the case of red-emitting CsPbI3 NCs. In this work, a new approach is proposed allowing the formation of red-emitting perovskite NCs by anion exchange induced directly inside a solid polymer matrix using green-emitting CsPbBr3 NCs as templates and iodododecane as an iodine source. Moreover, a simple and efficient route to photo-assisted termination of the anion exchange reaction in the polymer composite after reaching desired optical properties is demonstrated. The findings allow the authors to pattern a thin composite film with an ultrashort UV laser resulting in a selective generation of green- and red-emitting features with a 15 µm resolution

Excitonic improvement of colloidal nanocrystals in salt powder matrix for quality lighting and color enrichment

Here we report excitonic improvement in color-converting colloidal nanocrystal powders enabled by co-integrating nonpolar green-and red-emitting nanocrystal energy transfer pairs into a single LiCl salt matrix. This leads to nonradiative energy transfer (NRET) between the cointegrated nanocrystals in the host matrix. Here we systematically studied the resulting NRET process by varying donor and acceptor concentrations in the powders. We observed that NRET is a strong function of both of the nanocrystal concentrations and that NRET efficiency increases with increasing acceptor concentration. Nevertheless, with increasing donor concentration in the powders, NRET efficiency was found to first increase ( up to a maximum level of 53.9%) but then to decrease. As a device demonstrator, we employed these NRET-improved nanocrystal powders as color-converters on blue light-emitting diodes ( LEDs), with the resulting hybrid LED exhibiting a luminous efficiency > 70 lm/Welect. The proposed excitonic nanocrystal powders potentially hold great promise for quality lighting and color enrichment applications. (C) 2015 Optical Society of Americ

Dual-color emitting quantum-dot-quantum-well CdSe-ZnS heteronanocrystals hybridized on InGaN/GaN light emitting diodes for high-quality white light generation

Cataloged from PDF version of article.We report white light generation by hybridizing green-red emitting (CdSe)ZnS/CdSe (core)shell/shell quantum-dot-quantum-well heteronanocrystals on blue InGaN/GaN light emitting diodes with the photometric properties of tristimulus coordinates (x,y)=(0.36,0.30), luminous efficacy of optical radiation LE=278 lm/W, correlated color temperature CCT=3929 K, and color-rendering index CRI=75.1. We present the photometric analysis and the quantum mechanical design of these dual-color emitting heteronanocrystals synthesized to achieve high-quality white light when hybridized on light emitting diodes. Using such multicolor emitting heteronanocrystals facilitates simple device implementation while providing good photometric properties. (C) 2008 American Institute of Physics

Colloidal Nanocrystals Embedded in Macrocrystals: Robustness, Photostability, and Color Purity

Cataloged from PDF version of article.The incorporation of colloidal quantum dots (QDs) into ionic crystals of various salts (NaCl, KCl, KBr, etc.) is demonstrated. The resulting mixed crystals of various shapes and beautiful colors preserve the strong luminescence of the incorporated QDs. Moreover, the ionic salts appear to be very tight matrices, ensuring the protection of the QDs from the environment and as a result providing them with extraordinary high photo- and chemical stability. A prototype of a white light-emitting diode (WLED) with a color conversion layer consisting of this kind of mixed crystals is demonstrated. These materials may also find applications in nonlinear optics and as luminescence standards

trans-Dichloridotetrakis­[1-(2-hydroxy­ethyl)-1H-tetrazole-κN 4]cobalt(II)

The title cobalt(II) complex, [CoCl2(C3H6N4O)4], was obtained from metallic cobalt by direct synthesis. There are two Co atoms in the asymmetric unit, each lying on an inversion centre and adopting a distorted octa­hedral coordination. Classical and non-classical hydrogen bonds are responsible for formation of a three-dimensional polymeric network in the crystal