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High-Efficiency Light-Emitting Materials and Devices

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Optical and Photonic Materials".

Deadline for manuscript submissions: closed (20 September 2023) | Viewed by 6562

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Dr. Sangmoon Park

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Department of Energy and Chemical Engineering, Silla University, Busan 46958, Korea
Interests: phosphors; LEDs; structural-optical correlations; nanomaterials; photo-catalysts
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Down-conversion materials such as garnet phosphors and quantum dots combined with light-emitting-diode (LED) chips have changed the lighting and display industry by facilitating the highly efficient emission of white light. Up-conversion materials, which emit higher-energy visible photons from the excitation of lower-energy infrared photons, have also been widely applied to color displays, in optoelectronics, temperature sensors, biological imaging, and so on.LED devices incorporating organic and hybrid light-emitting materials such as perovskites have attained great achievements and gradually recognized commercialization. The search for new materials is driven by the need for highly energy-efficient materials and devices in many technologies. High-efficiency light-emitting materials and devices are studied in various areas of discovery. It is my pleasure to invite you to submit a manuscript on “High-efficiency light-emitting materials and devices”. Full papers, communications, and reviews are all welcome.

Dr. Sangmoon Park
Guest Editor

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Keywords

phosphors
garnets
perovskites
quantum dots
LEDs
devices

Published Papers (5 papers)

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Research

12 pages, 3668 KiB

Open AccessArticle

Intense Near-Infrared Light-Emitting NaYF₄:Nd,Yb-Based Nanophosphors for Luminescent Solar Concentrators

by A-Ra Hong, Seungyong Shin, Gumin Kang, Hyungduk Ko and Ho Seong Jang

Materials 2023, 16(8), 3187; https://doi.org/10.3390/ma16083187 - 18 Apr 2023

Viewed by 1110

Abstract

In this study, we synthesized NaYF₄-based downshifting nanophosphors (DSNPs), and fabricated DSNP-polydimethylsiloxane (PDMS) composites. Nd³⁺ ions were doped into the core and shell to increase absorbance at 800 nm. Yb³⁺ ions were co-doped into the core to achieve intense near-infrared (NIR) luminescence. To further enhance the NIR luminescence, NaYF₄:Nd,Yb/NaYF₄:Nd/NaYF₄ core/shell/shell (C/S/S) DSNPs were synthesized. The C/S/S DSNPs showed a 3.0-fold enhanced NIR emission at 978 nm compared with core DSNPs under 800 nm NIR light. The synthesized C/S/S DSNPs showed high thermal stability and photostability against the irradiation with ultraviolet light and NIR light. Moreover, for application as luminescent solar concentrators (LSCs), C/S/S DSNPs were incorporated into the PDMS polymer, and the DSNP-PDMS composite containing 0.25 wt% of C/S/S DSNP was fabricated. The DSNP-PDMS composite showed high transparency (average transmittance = 79.4% for the visible spectral range of 380–750 nm). This result demonstrates the applicability of the DSNP-PDMS composite in transparent photovoltaic modules. Full article

(This article belongs to the Special Issue High-Efficiency Light-Emitting Materials and Devices)

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14 pages, 5777 KiB

Open AccessEditor’s ChoiceArticle

Lanthanide and Ladder-Structured Polysilsesquioxane Composites for Transparent Color Conversion Layers

by Jaehyun Han, Darya Burak, Valeriia Poliukhova, Albert S. Lee, Hoseong Jang, Seungsang Hwang, Kyung-Youl Baek, Joonsoo Han, Byeong-Kwon Ju and So-Hye Cho

Materials 2023, 16(6), 2537; https://doi.org/10.3390/ma16062537 - 22 Mar 2023

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Abstract

Ladder-type polysilsesquioxanes (LPSQs) containing phenyl as a high refractive index unit and cyclic epoxy as a curable unit were found to be excellent candidates for a transparent color conversion layer for displays due to being miscible with organic solvents and amenable to transparent film formation. Therefore, the LPSQs were combined with luminescent lanthanide metals, europium Eu(III), and terbium Tb(III), to fabricate transparent films with various emission colors, including red, orange, yellow, and green. The high luminescence and transmittance properties of the LPSQs–lanthanide composite films after thermal curing were attributed to chelating properties of hydroxyl and polyether side chains of LPSQs to lanthanide ions, as well as a light sensitizing effect of phenyl side chains of the LPSQs. Furthermore, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy and nanoindentation tests indicated that the addition of the nanoparticles to the LPSQs moderately enhanced the epoxy conversion rate and substantially improved the wear resistance, including hardness, adhesion, and insusceptibility to atmospheric corrosion in a saline environment. Thus, the achieved LPGSG–lanthanide hybrid organic–inorganic material could effectively serve as a color conversion layer for displays. Full article

(This article belongs to the Special Issue High-Efficiency Light-Emitting Materials and Devices)

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11 pages, 4078 KiB

Open AccessArticle

Monolithic Multicolor Emissions of InGaN-Based Hybrid Light-Emitting Diodes Using CsPbBr₃ Green Quantum Dots

by Jae-Hyeok Oh, Seung-Beom Cho, Il-Kyu Park and Sung-Nam Lee

Materials 2023, 16(3), 1290; https://doi.org/10.3390/ma16031290 - 02 Feb 2023

Viewed by 1353

Abstract

To address the increasing demand for multicolor light-emitting diodes (LEDs), a monolithic multicolor LED with a simple process and high reliability is desirable. In this study, organic–inorganic hybrid LEDs with violet and green wavelengths were fabricated by depositing CsPbBr₃ perovskite green quantum dots (QDs) as the light-converting material on InGaN-based violet LEDs. As the injection current was increased, the total electroluminescence (EL) intensities of the hybrid LEDs increased, whereas the light-converted green emission efficiency of the CsPbBr₃ QDs decreased. The maximum green-to-violet EL spectral intensity ratio of the hybrid LEDs with CsPbBr₃ QDs was achieved with the injection current of <10 mA. Moreover, the EL spectral ratio of the green-to-violet emission decreased at an injection current of 100 mA. The light-conversion intensity of the CsPbBr₃ QDs decreased linearly as the junction temperature of the hybrid LEDs was increased with increasing injection current, similar to the temperature-dependent photoluminescence degradation of CsPbBr₃ QDs. In addition, the junction temperature of the hybrid LED was minimized by pulse injection to suppress the thermal degradation of QDs and increase the light conversion efficiency to green emission. Therefore, the overall emission spectrum color coordinates of the hybrid LEDs exhibited a red shift from violet to blue in the low-current region and a blue shift toward violet as the green emission of the QDs was decreased above 10 mA. Full article

(This article belongs to the Special Issue High-Efficiency Light-Emitting Materials and Devices)

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8 pages, 1162 KiB

Open AccessArticle

Co-Doping Effect on the Optical Properties of Eu^(2+/3+) Doped in BaSiO₃

by Purevdulam Namkhai and Kiwan Jang

Materials 2022, 15(19), 6559; https://doi.org/10.3390/ma15196559 - 21 Sep 2022

Cited by 1 | Viewed by 852

Abstract

To investigate the effect of co-doping on the optical properties of Eu^(2+/3+) doped in Ba₀.₉₈SiO₃:0.02Eu, the series of Ba₀.₉₆SiO₃:0.02Eu, 0.02R^+/3+ (R⁺ = Li⁺, K⁺ or [...] Read more.

To investigate the effect of co-doping on the optical properties of Eu^(2+/3+) doped in Ba₀.₉₈SiO₃:0.02Eu, the series of Ba₀.₉₆SiO₃:0.02Eu, 0.02R^+/3+ (R⁺ = Li⁺, K⁺ or Na⁺, R³⁺ = La³⁺ or Y³⁺) phosphors were synthesized using a solid-state reaction method. The excitation efficiency due to the charge transfer band (CTB) was enhanced via co-doping of R⁺ and the emission intensity due to Eu³⁺ was thus increased by 3.7 times compared with that of the single-doped Ba₀.₉₈SiO₃:0.02Eu³⁺. However, the co-doping of R⁺ does not increase the emission intensity of Eu³⁺ via the direct ⁷F₀→⁵L₆ excitation of Eu³⁺, but rather decreases it. On the other hand, the emission intensities due to Eu²⁺ were decreased via the co-doping of R⁺ but increased via the co-doping of La³⁺. The present work reveals that the optical properties of Eu³⁺ or Eu²⁺ doped in BaSiO₃ depend not on the charge state (+ or 3+) of the co-doped ions, but on the co-doped element itself. Full article

(This article belongs to the Special Issue High-Efficiency Light-Emitting Materials and Devices)

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9 pages, 1116 KiB

Open AccessArticle

Nonstoichiometric LaO_0.65F_1.7 Structure and Its Green Luminescence Property Doped with Bi³⁺ and Tb³⁺ Ions for Applying White UV LEDs

by Sungjun Yang, Seungyong Shin, Heonji Ha and Sangmoon Park

Materials 2022, 15(12), 4222; https://doi.org/10.3390/ma15124222 - 14 Jun 2022

Cited by 1 | Viewed by 1196

Abstract

Red–green–blue phosphors excited by ultraviolet (UV) radiation for white light LEDs have received much attention to improve the efficiency, color rendering index (CRI), and chromatic stability. The spectral conversion of a rare-earth ion-doped nonstoichiometric LaO_0.65F_1.7 host was explored with structural analysis in this report. The nonstoichiometric structure of a LaO_0.65F_1.7 compound, synthesized by a solid-state reaction using La₂O₃ and excess NH₄F precursors, was analyzed by synchrotron X-ray powder diffraction. The crystallized LaO_0.65F_1.7 host, which had a tetragonal space group of P4/nmm, contained 9- and 10-coordinated La³⁺ sites. Optical materials composed of La_1−p−_qBi_pTb_qO_0.65F_1.7 (p = 0 and 0.01; q = 0–0.2) were prepared at 1050 °C for 2 h, and the single phase of the obtained phosphors was indexed by X-ray diffraction analysis. The photoluminescence spectra of the energy transfer from Bi³⁺ to Tb³⁺ were obtained upon excitation at 286 nm in the nonstoichiometric host lattice. The desired Commission Internationale de l’Eclairage (CIE) values of the phosphors were calculated. The intense green La_0.89Bi_0.01Tb_0.1O_0.65F_1.7 phosphor with blue and red optical materials was fabricated on a 275 nm UV-LED chip, resulting in white light, and the internal quantum efficiency, CRI, correlated color temperature, and CIE of the pc LED were characterized. Full article

(This article belongs to the Special Issue High-Efficiency Light-Emitting Materials and Devices)

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