Study on Reabsorption Properties of Quantum Dot Color Convertors for Light-Emitting Diode Packaging

Abstract Quantum dot (QD) attracts great attention in light-emitting diode (LED) packaging for high-quality light sources, while it leads to low light efficiency due to the significantly high reabsorption loss between QDs. Accordingly, we experimentally study the reabsorption properties of QD color convertors (QCCs) for LED packaging considering various thicknesses and concentrations under different injection current. The results indicate the QCC configuration with a small thickness and large concentration can have the same absorption ability for chip light as that with the opposite configuration, resulting in the same QD light proportion. However, the QCC configuration having smaller thickness is more useful to decrease the reabsorption loss, leading to higher radiant power (an increase of larger than 37.2%). Moreover, it is essential to gain a high radiant power of QD light with small reabsorption loss, which can be realized by combining QCCs with a low QD content and a source with a large injection current. Based on this simple and effective approach, a conversion loss smaller than 20%, close to their quantum yield, can be achieved, which is approximately four times smaller than that gained by QCCs with a high QD content. However, it introduces additional radiant power of chip light, suppressing further improvement in the QD light proportion. Much work is still required to make full use of the redundant chip light. This study provides a better understanding of the reabsorption properties of QCCs and can significantly accelerate their applications in illumination and display applications.

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Low-Coherence Digital Holography for Enhanced 3D Measurement

ASME-JSME 2018 Joint International Conference on Information Storage and Processing Systems and Micromechatronics for Information and Precision Equipment ◽

10.1115/isps-mipe2018-8518 ◽

2018 ◽

Author(s):

No-Cheol Park ◽

Sungbin Jeon ◽

Jae-Yong Lee ◽

Se-Hwan Jang ◽

Jang-Hyun Cho ◽

...

Keyword(s):

Quantum Dot ◽

Digital Holography ◽

Light Emitting Diode ◽

Speckle Noise ◽

Light Sources ◽

Light Emitting ◽

Low Coherence ◽

Quantitative Measurements ◽

System Configurations ◽

Conventional Systems

In this paper, phase quantitative measurements using digital holography (DH) with low-coherence light sources are presented. Compared with conventional laser-based DH, low-coherence light sources have advantages of better image quality, less speckle noise, and smaller system configurations. As a light source, we utilized light-emitting diode (LED) and quantum dot (QD) film. In particular, quantum dot film emits low-coherence lights with adjustable wavelength and high conversion efficiency, which has versatility for additional methods including dual-wavelength reconstruction. Experimental results verify the quality enhanced quantitative measurement of proposed methods compared with conventional systems.

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Geranium and Purple Fountain Grass Leaf Pigmentation Is Influenced by End-of-Production Supplemental Lighting with Red and Blue Light-emitting Diodes

HortScience ◽

10.21273/hortsci11098-16 ◽

2017 ◽

Vol 52 (2) ◽

pp. 236-244 ◽

Cited By ~ 3

Author(s):

W. Garrett Owen ◽

Roberto G. Lopez

Keyword(s):

Chlorophyll Content ◽

Light Emitting Diode ◽

Red Light ◽

Light Sources ◽

Low Light ◽

Light Emitting ◽

Pennisetum Setaceum ◽

Hue Angle ◽

Supplemental Lighting ◽

Relative Chlorophyll Content

Under low-light greenhouse conditions, anthocyanin pigmentation in vegetative tissues of red- or purple-leafed floricultural crops is not fully expressed and, consequently, plants are not as visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; before shipping) supplemental lighting (SL) of different light sources, qualities, and intensities on foliage color of geranium (Pelargonium ×hortorum L.H. Bailey ‘Black Velvet’) and purple fountain grass [Pennisetum ×advena Wipff and Veldkamp (formerly known as Pennisetum setaceum Forsk. Chiov. ‘Rubrum’)]. Plants were finished under early (Expt. 1) and late (Expt. 2) seasonal greenhouse ambient solar light and provided with 16 hours of day-extension lighting from low-intensity light-emitting diode (LED) lamps [7:11:33:49 blue:green:red:far-red light ratio (%); control] delivering 4.5 μmol·m−2·s−1, or 16 hours of EOP SL from high-pressure sodium (HPS) lamps delivering 70 μmol·m−2·s−1, or LED arrays (100:0, 87:13, 50:50, or 0:100 red:blue) delivering 100 μmol·m−2·s−1, or 0:100 red:blue LEDs delivering 25 or 50 μmol·m−2·s−1. Geranium and fountain grass chlorophyll content and leaf color were estimated using a SPAD-502 chlorophyll meter and Minolta tristimulus colorimeter, respectively. Relative chlorophyll content (RCC) and foliage L* (lightness), C* (chroma; a measure of saturation), and h° (hue angle; a measure of tone) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of geranium and fountain grass increased from 3 to 14 days of exposure to EOP SL from HPS lamps and LEDs delivering 100 μmol·m−2·s−1. Under low daily light integrals (DLIs) [8.6 mol·m−2·d−1 (geranium) and 9.4 mol·m−2·d−1 (purple fountain grass)] EOP SL providing 100 μmol·m−2·s−1 of 100:0, 87:13, 50:50, or 0:100 red:blue light for ≥14 days resulted in lower L* (darker foliage), C* (saturated), and h° (orange to violet-red hues). Our data indicate that a minimum of 14 days of EOP SL providing 100 μmol·m−2·s−1 of 50:50 or 0:100 red:blue light enhanced foliage color of geranium and fountain grass leaves when plants were grown under a low greenhouse DLI ≤ 9 mol·m−2·d−1.

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Response to White Light Emitting Diode Aviation Signal Lights Varying in Correlated Color Temperature

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198119834007 ◽

2019 ◽

Vol 2673 (3) ◽

pp. 667-675 ◽

Cited By ~ 2

Author(s):

John D. Bullough ◽

Yi-wei Liu

Keyword(s):

Light Emitting Diode ◽

Color Temperature ◽

Light Sources ◽

White Led ◽

Low Light ◽

Light Emitting ◽

Light Levels ◽

Relative Brightness ◽

Discomfort Glare ◽

Source Spectra

Airfield lighting for runways and taxiways is currently undergoing a transition from filament-based incandescent sources to light emitting diodes (LEDs). Although models to assess the relative brightness, discomfort glare, and peripheral detectability of signal lights such as those used for aviation exist, their applicability to white LED airfield lighting has not been verified independently. A series of three experiments was conducted to compare white LED sources, having correlated color temperatures of 2,700 K and 5,900 K, in terms of their relative brightness, discomfort glare, and peripheral detectability. The perceived brightness and discomfort glare from the light sources closely matched predictions from the published models, demonstrating the usefulness of these models at characterizing these responses in airfield lighting. In the case of peripheral detectability, there was little to no difference in how quickly the two LEDs were perceived at low light levels, suggesting that there is no need to consider spectral differences between light source spectra for this response when the intensities are similar to those used in the present study.

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Electro-ridge for large injection current of micro-size InGaN light emitting diode

10.1117/12.613306 ◽

2005 ◽

Author(s):

B. J. Pong ◽

C. H. Chen ◽

J. F. Hsu ◽

C. J. Tun ◽

G. C. Chi

Keyword(s):

Light Emitting Diode ◽

Injection Current ◽

Light Emitting ◽

Large Injection

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Synchronization of Chaotic Quantum Dot Light Emitting Diodes under Optical Feedback Effect

10.32792/utq/utjsci/vol7/2/31 ◽

2020 ◽

pp. 144-148

Keyword(s):

Quantum Dot ◽

Delay Time ◽

Chaos Synchronization ◽

Optical Feedback ◽

Light Emitting Diode ◽

Feedback Effect ◽

Complete Synchronization ◽

Light Emitting ◽

Coupling Methods ◽

Coupling Parameters

Chaos synchronization of delayed quantum dot light emitting diode has been studied theortetically which are coupled via the unidirectional and bidirectional. at synchronization of chaotic, The dynamics is identical with delayed optical feedback for those coupling methods. Depending on the coupling parameters and delay time the system exhibits complete synchronization, . Under proper conditions, the receiver quantum dot light emitting diode can be satisfactorily synchronized with the transmitter quantum dot light emitting diode due to the optical feedback effect.

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