Special Issue "Solid State Lighting"

A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (15 September 2017).

Special Issue Editors

Prof. Hsiang-Chen Wang
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Guest Editor
Graduate Institute of Opto-Mechatronics and Advanced Institute of Manufacturing with High -tech Innovations, Taiwan
Interests: intelligent image recognition; biomedical imaging and sensing
Special Issues and Collections in MDPI journals
Prof. Ya-Ju Lee
Website
Guest Editor
Graduate Institute and Undergraduate Program of Electro-Optical Engineering, National Taiwan Normal University
Interests: nanophotonics devices, optoelectronic devices, compound semiconductors
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

The Nobel Prize in Physics 2014 was awarded “for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources". Due to the fact that one fourth of electricity use in the world is for lighting, LED lights can contribute in vastly reducing energy usage in the world. Moreover, LED lights can be used for up to 100,000 hours, compared to 1000 hours for incandescent lights, and 10,000 hours of fluorescent lights, and, thus, can also greatly reduce resource costs. Progress in solid state lightings required innovations in devices and concepts in order to achieve energy-saving and environmental-protecting capabilities. In this Special Issue, the Guest Editors attempt to bring some of the recent technological advances in UV LEDs, micro-LED, QD-LED, blue laser, new materials, smart lighting, and color lighting with the goal of achieving energy-saving.

Prof. Dr. Hsiang-Chen Wang
Prof. Dr. Ya-Ju Lee
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • UV LEDs
  • micro-LED
  • QD-LED
  • blue laser
  • new materials
  • smart lighting
  • and color lighting

Published Papers (6 papers)

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Research

Open AccessArticle
LED Uniform Illumination Using Double Linear Fresnel Lenses for Energy Saving
Energies 2017, 10(12), 2091; https://doi.org/10.3390/en10122091 - 11 Dec 2017
Cited by 7
Abstract
We present a linear Fresnel lens design for light-emitting diode (LED) uniform illumination applications. The LED source is an array of LEDs. An array of collimating lens is applied to collimate output from the LED array. Two linear Fresnel lenses are used to [...] Read more.
We present a linear Fresnel lens design for light-emitting diode (LED) uniform illumination applications. The LED source is an array of LEDs. An array of collimating lens is applied to collimate output from the LED array. Two linear Fresnel lenses are used to redistribute the collimated beam along two dimensions in the illumination area. Collimating lens and linear Fresnel lens surfaces are calculated by geometrical optics and nonimaging optics. The collimated beam output from the collimating lens array is divided into many fragments. Each fragment is refracted by a segment of Fresnel lens and distributed over the illumination area, so that the total beam can be distributed to the illumination target uniformly. The simulation results show that this design has a compact structure, high optical efficiency of 82% and good uniformity of 76.9%. Some consideration of the energy savings and optical performance are discussed by comparison with other typical light sources. The results show that our proposed LED lighting system can reduce energy consumption five-times in comparison to using a conventional fluorescent lamp. Our research is a strong candidate for low cost, energy savings for indoor and outdoor lighting applications. Full article
(This article belongs to the Special Issue Solid State Lighting)
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Open AccessArticle
Magnetron Sputter Epitaxy of High-Quality GaN Nanorods on Functional and Cost-Effective Templates/Substrates
Energies 2017, 10(9), 1322; https://doi.org/10.3390/en10091322 - 02 Sep 2017
Cited by 12
Abstract
We demonstrate the versatility of magnetron sputter epitaxy by achieving high-quality GaN nanorods on different substrate/template combinations, specifically Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti. Growth temperature was optimized on Si, TiN/Si, and ZrB2/Si, resulting in [...] Read more.
We demonstrate the versatility of magnetron sputter epitaxy by achieving high-quality GaN nanorods on different substrate/template combinations, specifically Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti. Growth temperature was optimized on Si, TiN/Si, and ZrB2/Si, resulting in increased nanorod aspect ratio with temperature. All nanorods exhibit high purity and quality, proved by the strong bandedge emission recorded with cathodoluminescence spectroscopy at room temperature as well as transmission electron microscopy. These substrates/templates are affordable compared to many conventional substrates, and the direct deposition onto them eliminates cumbersome post-processing steps in device fabrication. Thus, magnetron sputter epitaxy offers an attractive alternative for simple and affordable fabrication in optoelectronic device technology. Full article
(This article belongs to the Special Issue Solid State Lighting)
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Open AccessArticle
The Effect of Imbalanced Carrier Transport on the Efficiency Droop in GaInN-Based Blue and Green Light-Emitting Diodes
Energies 2017, 10(9), 1277; https://doi.org/10.3390/en10091277 - 27 Aug 2017
Cited by 11
Abstract
The effect of strongly-imbalanced carrier concentration and mobility on efficiency droop is studied by comparing the onset voltage of high injection, the onset current density of the droop, and the magnitude of the droop, as well as their temperature dependence, of GaInN-based blue [...] Read more.
The effect of strongly-imbalanced carrier concentration and mobility on efficiency droop is studied by comparing the onset voltage of high injection, the onset current density of the droop, and the magnitude of the droop, as well as their temperature dependence, of GaInN-based blue and green light-emitting diodes (LEDs). An n-to-p asymmetry factor is defined as σn/σp, and was found to be 17.1 for blue LEDs and 50.1 for green LEDs. Green LEDs, when compared to blue LEDs, were shown to enter the high-injection regime at a lower voltage, which is attributed to their less favorable p-type transport characteristics. Green LEDs, with lower hole concentration and mobility, have a lower onset current density of the efficiency droop and a higher magnitude of the efficiency droop when compared to blue LEDs. The experimental results are in quantitative agreement with the imbalanced carrier transport causing the efficiency droop, thus providing guidance for alleviating the phenomenon of efficiency droop. Full article
(This article belongs to the Special Issue Solid State Lighting)
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Open AccessArticle
The Effect of Solvents on the Performance of CH3NH3PbI3 Perovskite Solar Cells
Energies 2017, 10(5), 599; https://doi.org/10.3390/en10050599 - 29 Apr 2017
Cited by 21
Abstract
The properties of perovskite solar cells (PSCs) fabricated using various solvents was studied. The devices had an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/CH3NH3PbI3 (fabricated by using various solvents)/fullerene (C60)/bathocuproine (BCP)/silver (Ag) structure. The solvents used were [...] Read more.
The properties of perovskite solar cells (PSCs) fabricated using various solvents was studied. The devices had an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/CH3NH3PbI3 (fabricated by using various solvents)/fullerene (C60)/bathocuproine (BCP)/silver (Ag) structure. The solvents used were dimethylformamide (DMF), γ-butyrolactone (GBL), dimethyl sulfoxide (DMSO), a mixture of DMSO and DMF (1:1 v/v), and a mixture of DMSO and GBL (DMSO: GBL, 1:1 v/v), respectively. The power conversion efficiency (PCE) of the device fabricated using DMF is zero, which is attributed to the poor coverage of CH3NH3PbI3 film on the substrate. In addition, the PCE of the device made using GBL is only 1.74% due to the low solubility of PbI2 and CH3NH3I. In contrast, the PCE of the device fabricated using the solvents containing DMSO showed better performance. This is ascribed to the high solubilization properties and strong coordination of DMSO. As a result, a PCE of 9.77% was obtained using a mixed DMSO:GBL solvent due to the smooth surface, uniform film coverage on the substrate and the high crystallization of the perovskite structure. Finally, a mixed DMSO: DMF:GBL (5:2:3 v/v/v) solvent that combined the advantages of each solvent was used to fabricate a device, leading to a further improvement of the PCE of the resulting PSC to 10.84%. Full article
(This article belongs to the Special Issue Solid State Lighting)
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Open AccessArticle
How Smart LEDs Lighting Benefit Color Temperature and Luminosity Transformation
Energies 2017, 10(4), 518; https://doi.org/10.3390/en10040518 - 11 Apr 2017
Cited by 14
Abstract
Luminosity and correlated color temperature (CCT) have gradually become two of the most important factors in the evaluation of the performance of light sources. However, although most color performance evaluation metrics are highly correlated with CCT, these metrics often do not account for [...] Read more.
Luminosity and correlated color temperature (CCT) have gradually become two of the most important factors in the evaluation of the performance of light sources. However, although most color performance evaluation metrics are highly correlated with CCT, these metrics often do not account for light sources with different CCTs. This paper proposes the existence of a relationship between luminosity and CCT to remove the effects of CCT and to allow for a fairer judgment of light sources under the current color performance evaluation metrics. This paper utilizes the Hyper-Spectral Imaging (HSI) technique to recreate images of a standard color checker under different luminosities, CCT, and light sources. The images are then analyzed and transformed into interpolation figures and equal color difference curves. This paper utilizes statistic tools and symmetry properties to determine an exponential relationship between luminosity and CCT in red-green-blue (RGB) LED and OLED light sources. Such a relationship presents an option to remove the effects of CCT in color evaluation standards, as well as provide a guide line for adjusting visual experience solely by adjusting luminosity when creating a lighting system. Full article
(This article belongs to the Special Issue Solid State Lighting)
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Open AccessArticle
Scale-Dependent Light Scattering Analysis of Textured Structures on LED Light Extraction Enhancement Using Hybrid Full-Wave Finite-Difference Time-Domain and Ray-Tracing Methods
Energies 2017, 10(4), 424; https://doi.org/10.3390/en10040424 - 23 Mar 2017
Cited by 7
Abstract
A multiscale model that enables quantitative understanding and prediction of the size effect on the scattering properties of micro- and nanostructures is crucial for the design of light-emitting diode (LED) surface textures optimized for high light extraction efficiency (LEE). In this paper, a [...] Read more.
A multiscale model that enables quantitative understanding and prediction of the size effect on the scattering properties of micro- and nanostructures is crucial for the design of light-emitting diode (LED) surface textures optimized for high light extraction efficiency (LEE). In this paper, a hybrid process for combining full-wave finite-difference time-domain simulation and a ray-tracing technique based on a bidirectional scattering distribution function model is proposed. We apply this method to study the influence of different pattern sizes of a patterned sapphire substrate on GaN-based LED light extraction from the micro-scale to the nano-scale. The results show that near-wavelength–scale patterns with strong diffraction are not expected to enhance the LEE. By contrast, micro-scale patterns with optical diffusion behavior have the highest LEE at a specific aspect ratio, and subwavelength-scale patterns that have antireflection properties show a marked enhancement of the LEE for a wide range of aspect ratios. Full article
(This article belongs to the Special Issue Solid State Lighting)
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