Efficiency droop improvement in InGaN light-emitting diodes with graded InGaN barriers of increasing indium composition

2015 ◽  
Vol 118 (10) ◽  
pp. 103103 ◽  
Author(s):  
Liwen Cheng ◽  
Shudong Wu ◽  
Changquan Xia ◽  
Haitao Chen
Keyword(s):  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Emitting ◽  
Indium Composition

Asymmetry of carrier transport leading to efficiency droop in GaInN based light-emitting diodes

2011 ◽  
Vol 99 (25) ◽  
pp. 251115 ◽  
Author(s):  
David S. Meyaard ◽  
Guan-Bo Lin ◽  
Qifeng Shan ◽  
Jaehee Cho ◽  
E. Fred Schubert ◽  
...  
Keyword(s):  
Carrier Transport ◽  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Emitting

Improvement of efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes with trapezoidal wells

2010 ◽  
Vol 43 (35) ◽  
pp. 354004 ◽  
Author(s):  
Sang-Heon Han ◽  
Dong-Yul Lee ◽  
Hyun-Wook Shim ◽  
Gwon-Chul Kim ◽  
Young Sun Kim ◽  
...  
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Multiple Quantum Well ◽  
Efficiency Droop ◽  
Multiple Quantum ◽  
Light Emitting

Approaches Towards the Ultimate Luminous Output Power of Light-Emitting Diodes: Bottlenecks and Remedies

2015 ◽  
Author(s):  
Xiaokun Zhang ◽  
Xiao-Dong Xiang ◽  
Yong Xiang
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Thermal Runaway ◽  
Efficiency Droop ◽  
Injection Current ◽  
Light Emitting ◽  
Excessive Heat ◽  
High Injection ◽  
Current Densities ◽  
The Cost

Although light-emitting diodes (LEDs) hold great promises for high-efficiency lighting applications, the cost per lumen still poses a challenge for LEDs to fast penetrate into the markets. Increasing the output power per LED chip reduces the number of chips required for a specific luminous flux, thus reducing the cost of LED luminaires. However, it is well known that the luminous output power of LEDs (Pout) cannot be enhanced simply by increasing the injection current density (Jinj) due to efficiency droop. Extensive efforts have been made towards avoiding efficiency droop at high injection current densities (e.g., Jinj > 50 A/cm2). Gardner et al. reported a double-heterostructure LED with an external quantum efficiency (EQE) of 40% at 200 A/cm2. Xie et al. introduced an electron-blocking layer into the LED devices and the EQE peak occurred at 900 A/cm2 approximately. Nevertheless, the EQE is always lower than 100%, excessive heat will accumulate in LEDs at high current densities and increase the junction temperatures, which will damage the device and limit its luminous output power and lifetime. In this paper, the recombination mechanism in the LED active area is analyzed and an analytic relationship between Pout and Jinj is proposed. The calculated results show that the best Pout currently achieved is far lower than its potential value. The temperature dependence of the Pout-Jinj relationship is also calculated and the thermal state of LEDs at high injection current densities predicted. The results demonstrate that LED luminaires with thermal management based on conventional fin-shaped heat sinks suffer from thermal runaway due to excessive heat accumulation before reaching their ultimate output power. The gap between the existing and predicted Pout is mainly due to thermal runaway of LED devices at high injection current densities, instead of efficiency droop. Therefore, the short-term solution of LED luminous output power enhancement should be better cooling of LED modules, such as jet/spray cooling, heat pipe cooling, or 3D embedded two-phase cooling. Long-term solutions continue to focus on reducing the efficiency droop with improved LED device structures and advanced materials.

Temperature-dependent efficiency droop behaviors of GaN-based green light-emitting diodes

2013 ◽  
Vol 22 (4) ◽  
pp. 047805 ◽  
Author(s):  
Rong Jiang ◽  
Hai Lu ◽  
Dun-Jun Chen ◽  
Fang-Fang Ren ◽  
Da-Wei Yan ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Green Light ◽  
Efficiency Droop ◽  
Temperature Dependent ◽  
Light Emitting
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