Hybrid ZnO nanophosphors assembled in mesosphere for LED application.

National audienc

Luminescent Nanocomposites Made of Finely Dispersed Y₃Ga₅O₁₂:Tb Powder in a Polymer Matrix: Promising Candidates for Optical Devices

This paper reports the initial results of an original and simple method to elaborate flexible, self-standing, and thick luminescent films suitable for optical devices. PVP/Y₃Ga₅O₁₂:Tb³⁺ nanocomposite films have been successfully achieved from a sol–gel derived Y₃Ga₅O₁₂:Tb³⁺ powder and an alcoholic solution of poly-<i>N</i>-vinylpyrrolidone (PVP). The structural, morphological, and optical properties of these nanocomposite films have been studied and compared to those of a pristine PVP film and Y₃Ga₅O₁₂:Tb³⁺ powder. The nanocomposite films were characterized by infrared and Raman spectroscopies as well as scanning and transmission electron microscopies (SEM and TEM) and demonstrated good dispersion of the phosphor particles within the polymer matrix via an alveolar mesostructure. The optical properties of these nanocomposites were fully characterized, and both their excitation and emission spectra and decay curves were recorded. Furthermore, photostability of the nanocomposite films and of the luminescent raw powder has been studied after exposure to an accelerated artificial photoageing at wavelengths higher than 300 nm. The elaboration process used is both tunable and applicable to a large variety of powders and polymers because it does not require any additive to form homogeneous and easily shapeable phosphor/polymer nanocomposites applicable in a large variety of optical devices such as solid-state-lighting

Solution processing of hybrid ZnO nanophosphors assembled in mesosphere for LED applications

National audienc

Solution processing of hybrid ZnO nanophosphors assembled in mesosphere for LED applications

National audienc

Optical Properties and Reliability Studies of Gradient Alloyed Green Emitting (CdSe)_<i>x</i>(ZnS)_1–<i>x</i> and Red Emitting (CuInS₂)_<i>x</i>(ZnS)_1–<i>x</i> Quantum Dots for White Light-Emitting Diodes

Luminescent materials become one of interesting issues for white LED-based lighting devices (WLEDs) due to their high performances for converting the monochromatic light from UV/blue LED chips into white light. Nevertheless, the availability of rare earth materials, the low color rendering index (CRI) and too-cold color temperature of the white LEDs remain some drawbacks to penetrate into the general LED lighting markets. Herein, we report the development of rare-earth-free luminescent nanocomposites combined with a UV/blue LED chip in order to provide white light. Gradient alloyed cadmium selenide/zinc sulfide (CdSe)_<i>x</i>(ZnS)_1–<i>x</i> and copper indium sulfide/zinc sulfide (CuInS₂)_<i>x</i>(ZnS)_1–<i>x</i> quantum dots have been used to achieve the luminescent nanocomposite films in silicone as polymer matrix. The optical performances were investigated upon LED excitation. The photometric parameters of systems consisting of luminescent nanocomposites and LEDs including color rendering index (CRI), correlated color temperature (CCT), Commission Internationale de l’Eclairage (CIE) chromaticity coordinates, and luminous efficacy can be tuned by controlling the compositions and thickness of nanocomposite films. Furthermore, the thermal stability and the reliability of these luminescent nanocomposite films were investigated

Ce-Doped YAG Nanophosphor and Red Emitting CuInS₂/ZnS Core/Shell Quantum Dots for Warm White Light-Emitting Diode with High Color Rendering Index

In this work, we report the solvothermal synthesis of Ce-doped YAG (YAG:Ce) nanoparticles (NPs) and their association with a free-Cd CuInS₂/ZnS (CIS/ZnS) core/shell QDs for application into white light emitting diode (WLED). 1500 °C-annealed YAG:Ce NPs and CIS/ZnS core/shell QDs exhibited intense yellow and red emissions band with maxima at 545 and 667 nm, respectively. Both YAG:Ce nanophosphor and CIS/ZnS QDs showed high photoluminescence quantum yield (PL QY) of about 50% upon 460 nm excitation. YAG:Ce nanophosphor layer and bilayered YAG:Ce nanophosphor-CIS/ZnS QDs were applied on blue InGaN chip as converter wavelength to achieve WLED. While YAG:Ce nanophosphor converter layer showed low color rendering index (CRI) and cold white light, bilayered YAG:Ce nanophosphor-CIS/ZnS QDs displayed higher CRI of about 84 and warm white light with a correlated color temperature (CCT) of 2784 K. WLED characteristics were measured as a function of forward current from 20 to 1200 mA. The white light stability of bilayered nanophosphor-QDs-based WLED operated at 200 mA was also studied as a function of operating time up to 40 h. Interestingly, CRI and CCT of such device tend to remain constant after 7 h of operating time suggesting that layer-by-layer structure of YAG:Ce phosphor and red-emitting CIS/ZnS QDs could be a good solution to achieve stable warm WLED, especially when high current density is applied

Projet SURFIN : nouveaux matériaux pour la SURveillance par Fibre optique des Installations Nucléaires

International audienc