The Optical Properties of Dual-Wavelength InxGa1−xN/GaN Nanorods for Wide-Spectrum Light-Emitting Diodes

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Jie Zhao ◽  
Xuecheng Wei ◽  
Dongdong Liang ◽  
Qiang Hu ◽  
Jianchang Yan ◽  
...  
Keyword(s):  
Stark Effect ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Internal Quantum Efficiency ◽  
Wide Spectrum ◽  
Dual Wavelength ◽  
Planar Structure ◽  
Nonradiative Recombination ◽  
Light Emitting ◽  
White Leds

Abstract We fabricated the dual-wavelength InxGa1−xN/GaN nanorods for wide-spectrum light-emitting diodes (LEDs) by silica nanosphere lithography (SNL) technique. The emission properties of the dual-wavelength nanorods are characterized by micro-photoluminescence (micro-PL), cathodoluminescence (CL), and temperature-dependent PL (TDPL) measurements. Nanorod structure can effectively suppress quantum confined Stark effect (QCSE) compared with planar structure due to the strain relaxation. In addition, the internal quantum efficiency (IQE) of the green quantum well (QW) within nanorod structure increases, but the IQE of the blue QW clearly decreases because blue QW has severely suffered from the nonradiative recombination by surface damage. Furthermore, the IQEs of the green QW and the blue QW within the nanorod structure can be effectively improved by wet etching treatment, with an increase in factor by 1.3 when compared with unetched nanorod structure. Evidently, the dual-wavelength InxGa1−xN/GaN nanorods are beneficial to improve the optical performance compared with planar structure, presenting a potential to realize monolithic, high-efficiency, and cost-effective white LEDs.

scholarly journals Efficient and large-area all vacuum-deposited perovskite light-emitting diodes via spatial confinement

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peipei Du ◽  
Jinghui Li ◽  
Liang Wang ◽  
Liang Sun ◽  
Xi Wang ◽  
...  
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Scale Production ◽  
Nonradiative Recombination ◽  
Large Area ◽  
Spatial Confinement ◽  
Light Emitting ◽  
Large Scale Production

AbstractWith rapid advances of perovskite light-emitting diodes (PeLEDs), the large-scale fabrication of patterned PeLEDs towards display panels is of increasing importance. However, most state-of-the-art PeLEDs are fabricated by solution-processed techniques, which are difficult to simultaneously achieve high-resolution pixels and large-scale production. To this end, we construct efficient CsPbBr3 PeLEDs employing a vacuum deposition technique, which has been demonstrated as the most successful route for commercial organic LED displays. By carefully controlling the strength of the spatial confinement in CsPbBr3 film, its radiative recombination is greatly enhanced while the nonradiative recombination is suppressed. As a result, the external quantum efficiency (EQE) of thermally evaporated PeLED reaches 8.0%, a record for vacuum processed PeLEDs. Benefitting from the excellent uniformity and scalability of the thermal evaporation, we demonstrate PeLED with a functional area up to 40.2 cm2 and a peak EQE of 7.1%, representing one of the most efficient large-area PeLEDs. We further achieve high-resolution patterned perovskite film with 100 μm pixels using fine metal masks, laying the foundation for potential display applications. We believe the strategy of confinement strength regulation in thermally evaporated perovskites provides an effective way to process high-efficiency and large-area PeLEDs towards commercial display panels.

Three-dimensional GaN dodecagonal ring structures for highly efficient phosphor-free warm white light-emitting diodes

Nanoscale ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 4686-4695 ◽  
Author(s):  
Young Chul Sim ◽  
Seung-Hyuk Lim ◽  
Yang-Seok Yoo ◽  
Min-Ho Jang ◽  
Sunghan Choi ◽  
...  
Keyword(s):  
White Light ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Three Dimensional ◽  
Light Emitting ◽  
White Leds ◽  
Highly Efficient ◽  
Warm White Light ◽  
Ring Structures ◽  
White Light Emitting Diodes

Multifaceted dodecagonal ring structures emit light of various colours with high efficiency and are demonstrated to be phosphor-free white LEDs.

scholarly journals Full-Color III-Nitride Nanowire Light-Emitting Diodes

2019 ◽  
Vol 3 (4) ◽  
pp. 551 ◽  
Author(s):  
Ravi Teja Velpula ◽  
Barsha Jain ◽  
Ha Quoc Thang Bui ◽  
Hieu Pham Trung Nguyen
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Current Status ◽  
Core Shell ◽  
Nonradiative Recombination ◽  
Carrier Distribution ◽  
Light Emitting ◽  
White Leds ◽  
Full Color

III-nitride nanowire-based light-emitting diodes (LEDs) have been intensively studied as promising candidates for future lighting technologies. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization fields, and quantum-conned Stark effect due to the effective lateral stress relaxation, promising high-efficiency full-color LEDs. Beside these advantages, however, several issues have been identified as the limiting factors for further enhancing the nanowire LED quantum efficiency and light output power. Some of the most probable causes have been identified as due to the lack of carrier confinement in the active region, non-uniform carrier distribution, electron overflow, and the nonradiative recombination along the nanowire lateral surfaces. Moreover, the presence of large surface states and defects contribute significantly to the carrier loss in nanowire LEDs. Consequently, reported nanowire LEDs show relatively low output power. Recently, III-nitride core-shell nanowire LED structures have been reported as the most efficient nanowire white LEDs with a record-high output power which is more than 500 times stronger than that of nanowire white LEDs without using core-shell structure. In this context, we will review the current status, challenges, and approaches for the high-performance IIInitride nanowire LEDs. More specifically, we will describe the current methods for the fabrication of nanowire structures including top-down and bottom-up approaches, followed by characteristics of III-nitride nanowire LEDs. We will then discuss the carrier dynamics and loss mechanism in nanowire LEDs. The typical designs for the enhanced performance of III-nitride nanowire LEDs will be presented next. The color-tunable nanowire LEDs with emission wavelengths in the visible spectrum and phosphor-free nanowire white LEDs will be finally discussed.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

scholarly journals Decreasing CCT deviation of white light emitting diodes by employing SiO2 nanoparticles

2021 ◽  
Vol 10 (3) ◽  
pp. 1316-1324
Author(s):  
My Hanh Nguyen Thi ◽  
Phung Ton That
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Internal Quantum Efficiency ◽  
Light Output ◽  
Sio2 Nanoparticles ◽  
Nano Particles ◽  
Light Extraction Efficiency ◽  
Light Emitting ◽  
White Leds ◽  
White Light Emitting Diodes

In this research, the SiO2 nano-particles (NPs) usage in enhancing optical performances of InGaN/GaN-based white light-emitting diodes (WLEDs) with remote phosphor structure. The research subject shows better lighting capacity than the white LEDs devices without the space between the layers. The adjustment in development process resulted in enhancements of internal quantum efficiency (IQE) and light extraction efficiency (LEE) that lead to 13.5% luminous efficacy improvement. From the experiments, it can be concluded that the LEE is affected by the trapped light and enhancing the light output with SiO2 scattering properties reduce the amount of trapped light. These results confirm that SiO2 nano-particles is effective in enhancing the optical performance of WLEDs and can be considered for production of higher quality devices.

scholarly journals A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire

2018 ◽  
Vol 8 (8) ◽  
pp. 1264 ◽  
Author(s):  
Yosuke Nagasawa ◽  
Akira Hirano
Keyword(s):  
Quantum Wells ◽  
Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Internal Quantum Efficiency ◽  
Threading Dislocation ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Light Emitting ◽  
Practical Applications ◽  
Deep Ultraviolet

This paper reviews the progress of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs), mainly focusing in the work of the authors’ group. The background to the development of the current device structure on sapphire is described and the reason for using a (0001) sapphire with a miscut angle of 1.0° relative to the m-axis is clarified. Our LEDs incorporate uneven quantum wells (QWs) grown on an AlN template with dense macrosteps. Due to the low threading dislocation density of AlGaN and AlN templates of about 5 × 108/cm2, the number of nonradiative recombination centers is decreased. In addition, the uneven QW show high external quantum efficiency (EQE) and wall-plug efficiency, which are considered to be boosted by the increased internal quantum efficiency (IQE) by enhancing carrier localization adjacent to macrosteps. The achieved LED performance is considered to be sufficient for practical applications. The advantage of the uneven QW is discussed in terms of the EQE and IQE. A DUV-LED die with an output of over 100 mW at 280–300 nm is considered feasible by applying techniques including the encapsulation. In addition, the fundamental achievements of various groups are reviewed for the future improvements of AlGaN-based DUV-LEDs. Finally, the applications of DUV-LEDs are described from an industrial viewpoint. The demonstrations of W/cm2-class irradiation modules are shown for UV curing.

scholarly journals Tuning the Resonant Frequency of a Surface Plasmon by Double-Metallic Ag/Au Nanoparticles for High-Efficiency Green Light-Emitting Diodes

2019 ◽  
Vol 9 (2) ◽  
pp. 305 ◽  
Author(s):  
Ryoya Mano ◽  
Dong-Pyo Han ◽  
Kengo Yamamoto ◽  
Seiji Ishimoto ◽  
Satoshi Kamiyama ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Internal Quantum Efficiency ◽  
Green Light ◽  
Resonance Wavelength ◽  
Resonant Wavelength ◽  
Emission Wavelength ◽  
Light Emitting ◽  
Green Leds

Currently, the internal quantum efficiency (IQE) of GaInN-based green light-emitting diodes (LEDs) is still low. To overcome this problem, surface plasmon (SP)-enhanced LEDs have been intensively studied for the last 15 years. For an SP effect in green LEDs, Au and Ag are typically employed as the plasmonic materials. However, the resonance wavelength is determined by their material constants, which are theoretically fixed at ~537 nm for Au and ~437 nm for Ag. In this study, we aimed to tune the SP resonant wavelength using double-metallic nanoparticles (NPs) composed of Au and Ag to match the SP resonance wavelength to the LED emission wavelength to consequently improve the IQE of green LEDs. To form double-metallic NPs, Au/Ag multilayers were deposited on a GaN layer and then thermally annealed. We changed the thicknesses of the multilayers to control the Ag/Au ratio in the NPs. We show that the SP resonant wavelength could be tuned using our approach. We also demonstrate that the enhancement of the IQE in SP-enhanced LEDs was strongly dependent on the SP resonant wavelength. Finally, the highest IQE was achieved by matching the SP resonant wavelength to the LED emission wavelength.

Implementation of LED Lighting Powered by Solar Energy for Bicycles

2021 ◽  
Vol 8 (5) ◽  
pp. 96-101
Author(s):  
Wen-Bin Lin ◽  
Kao-Feng Yarn
Keyword(s):  
Energy Saving ◽  
Environmental Protection ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Solar Photovoltaic ◽  
Light Emitting ◽  
Led Lighting ◽  
White Leds ◽  
The Future ◽  
Long Life

The high efficiency, simple driving, environmental protection and long life of high power white-light diodes have attracted a lot of attention from industry and academia. High-efficiency white LEDs have the potential to replace traditional lighting such as incandescent bulbs and fluorescent lamps, and can be used in residential environments, industry and commercial advertising. Because of the advantages of light-emitting diodes, such as power saving, environmental protection, long life and fast response time, they will replace traditional light-emitting elements as the new lighting source in the future. Under the restrictions and regulations of the Kyoto Protocol, we will cooperate with the country to actively promote energy-saving technology and energy industry in the future. This paper proposes the development of LED lighting and photovoltaic, and the application of solar photovoltaic systems to bicycles, in line with the green technology industry LED lighting and solar photovoltaic industry development. Energy-saving LEDs can be combined with stand-alone lighting systems to enable the sustainable development of renewable energy development and energy conservation policies in Taiwan. Keywords: Solar cells, Light-emitting diodes, LED lamp drivers, White LEDs.

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