Considerations on the Replacement of the Filament Lamp by Light Emitting Diodes (LED) on the External Vehicular Lighting

2011 ◽  
Author(s):  
Marcio Tibiri\ac\aa
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting ◽  
Filament Lamp

Full color carbon dots through surface engineering for constructing white light-emitting diodes

2019 ◽  
Vol 7 (8) ◽  
pp. 2212-2218 ◽  
Author(s):  
Wei Cai ◽  
Ting Zhang ◽  
Meng Xu ◽  
Miaoran Zhang ◽  
Yongjian Guo ◽  
...  
Keyword(s):  
White Light ◽  
Carbon Dots ◽  
Surface Engineering ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
Natural Sunlight ◽  
Filament Lamp ◽  
Full Color ◽  
White Light Emitting Diodes

White light-emitting diode (WLED) devices are replacing the filament lamp and can provide a light close to natural sunlight, and they have thus drawn considerable attention in recent years.

Thermal Analysis and Optimization of Light-Emitting Diodes Filament Lamp

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Jie Liu ◽  
Jinglong Zou ◽  
Sheng Liu
Keyword(s):  
Thermal Analysis ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Optimization Methods ◽  
Junction Temperature ◽  
Phosphor Layer ◽  
Light Emitting ◽  
Filament Lamp ◽  
Filament Lamps

Abstract Due to the high efficiency, light-emitting diodes (LED) filament lamps have become more and more popular alternative to the incandescent lamp. However, the heat generated by the LED chips is traditionally dissipated by relying on the natural convection within lamps, resulting in poor heat dissipation performance for LED filament lamps. A numerical simulation model of the typical LED filament lamp was established to simulate and analyze the heat dissipation and airflow phenomenon of LED filament lamps in this study. In addition, increasing lamp sizes, increasing phosphor diameters, and using finned phosphor layers were considered as optimization measures to improve the heat dissipation performance of LED filament lamps. When these optimization measures are applied, chip junction temperatures are reduced. A reduction of 6.9 °C is seen when the lamp radius is increased from 25 mm to 31 mm. When the phosphor diameter is increased to 4 mm from 2 mm, the junction temperature is reduced by 17.2 °C. Integration of a finned phosphor layer where there are 12 fins at a height of 1 mm and thickness of 0.2 mm in the layer decreased the junction temperature by 10.9 °C. These optimization results provide technical support for the design and manufacture of LED filament lamps, and thermal analysis results provide theoretical support for the promotion of these optimization methods.

Injecting Inter-Layers and the Built-in Potential of Blue Polymer Light-Emitting Diodes

2000 ◽  
Vol 660 ◽  
Author(s):  
Thomas M. Brown ◽  
Ian S. Millard ◽  
David J. Lacey ◽  
Jeremy H. Burroughes ◽  
Richard H. Friend ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Light Emitting Diodes ◽  
Basic Structure ◽  
Thin Layers ◽  
Carrier Injection ◽  
Semiconducting Polymer ◽  
Light Emitting ◽  
Physical Mechanisms ◽  
Organic Solid ◽  
Polymer Light Emitting Diodes

ABSTRACTThe semiconducting-polymer/injecting-electrode heterojunction plays a crucial part in the operation of organic solid state devices. In polymer light-emitting diodes (LEDs), a common fundamental structure employed is Indium-Tin-Oxide/Polymer/Al. However, in order to fabricate efficient devices, alterations to this basic structure have to be carried out. The insertion of thin layers, between the electrodes and the emitting polymer, has been shown to greatly enhance LED performance, although the physical mechanisms underlying this effect remain unclear. Here, we use electro-absorption measurements of the built-in potential to monitor shifts in the barrier height at the electrode/polymer interface. We demonstrate that the main advantage brought about by inter-layers, such as poly(ethylenedioxythiophene)/poly(styrene sulphonic acid) (PEDOT:PSS) at the anode and Ca, LiF and CsF at the cathode, is a marked reduction of the barrier to carrier injection. The electro- absorption results also correlate with the electroluminescent characteristics of the LEDs.

Low-Temperature Operation of Green, Blue and UV InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes

2003 ◽  
Vol 764 ◽  
Author(s):  
X. A. Cao ◽  
S. F. LeBoeuf ◽  
J. L. Garrett ◽  
A. Ebong ◽  
L. B. Rowland ◽  
...  
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Multiple Quantum Well ◽  
Light Output ◽  
Localized States ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
Light Emitting ◽  
Temperature Range ◽  
Green Leds

Absract:Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission energies ranging from 2.3 eV (green) to 3.3 eV (UV) has been studied over a wide temperature range (5-300 K). As the temperature is decreased from 300 K to 150 K, the EL intensity increases in all devices due to reduced nonradiative recombination and improved carrier confinement. However, LED operation at lower temperatures (150-5 K) is a strong function of In ratio in the active layer. For the green LEDs, emission intensity increases monotonically in the whole temperature range, while for the blue and UV LEDs, a remarkable decrease of the light output was observed, accompanied by a large redshift of the peak energy. The discrepancy can be attributed to various amounts of localization states caused by In composition fluctuation in the QW active regions. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. The large number of localized states in the green LEDs are crucial to maintain high-efficiency carrier capture at low temperatures.

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