Abstract
Efficiency droop in GaN-based light emitting diodes (LEDs) under high injection current density perplexes the development of high-power solid-state lighting. Although the relevant study has lasted for about 10 years, its mechanism is still not thoroughly clear, and consequently its solution is also unsatisfactory up to now. Some emerging applications, e.g., high-speed visible light communication, requiring LED working under extremely high current density, makes the influence of efficiency droop become more serious. This paper reviews the experimental measurements on LED to explain the origins of droop in recent years, especially some new results reported after 2013. Particularly, the carrier lifetime of LED is analyzed intensively and its effects on LED droop behaviors are uncovered. Finally, possible solutions to overcome LED droop are discussed.
Highlights
GaN-based light-emitting diodes (LEDs) have achieved remarkable developments in the last two decades
The present commercial LEDs have high enough efficiency, they are still suffering from the efficiency declining when injection current density increases, which is known as efficiency droop [5,6,7]
The I–V characteristic of both blue LED and green LED are examined and compared to each other. These comparisons confirmed the electron leakage model, which indicates that the onset of droop current density and the onset of high injection voltage will be lower while the magnitude of efficiency droop will be higher in LED with a greater imbalance in carrier concentration and mobility
Summary
GaN-based light-emitting diodes (LEDs) have achieved remarkable developments in the last two decades. They have already changed the human’s daily life significantly for their wide applications in liquid-crystal display (LCD) back-lighting, large screen display and general lighting [1,2,3]. The IQE of a LED under electrical injection is determined by both carrier radiative recombination efficiency (RRE). The former represents the proportion of carriers emitting light inside the active region while the latter denotes the proportion of carriers injected into the active region. Solutions to overcome droop effect are discussed based on the analysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
