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(December 2010) posted on Thu Dec 02, 2010

Essentials behind the LED market growths

By Dr. Nisa Khan

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As president of LED Lighting Technologies, Dr.Nisa Khan consults in the solid-state lighting industry and educates consumers about LED lighting. She has a bachelor’s degree in physics and mathematics, and master’s and Ph.D. degrees in electrical engineering. Email her at nisa.khan@iem-asset.com

The 2010 LED market appears to be exploding beyond projections – it’s now forecast to reach $9.1 billion, instead of $8.4 billion that Strategies Unlimited researchers projected 14 months ago. Much of the growth stems from the evolving use of LED-based backlight systems in LCD screens, but, interestingly, that specialty’s growth rate is predicted to slow, while the high-brightness LEDs (HBLED) market could double over the next four years, to reach $18.4 billion.

Although current LED-lamp systems easily integrate into signage, display backlighting and various other markets, HBLED technology needs to progress before it can meet (or exceed) broad-use lighting-market projections. The “needs attention” areas are:
 

1. The internal quantum efficiency (IQE) improvement at the LED-chip level, to (possibly) overcome the “droop” challenge that frustrates the industry. “Droop” defines the efficiency-drop phenomenon that occurs in LED lamps as electrical-power input is increased.
2. To overcome the directional nature of LEDs. Significantly more uniform light distribution is required for general lighting applications.
3. To increase LED lifespan through better thermal management.
4. To identify critical cost factors and reduce LED production costs.
    

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I’ve focused on three and four in previous columns and will revisit them with new information in the future, and, I’ll get into the directional problem within the next few months. Most importantly, in this column, I want to discuss the first subject –“droop” -- and propose some new reasons for it, with verification ideas.
 

Higher LED chip efficiency
White LEDs are most widely used for signage, display illumination and lighting applications. The most commonly used technology for white LEDs comprises nitride-based, i.e., gallium nitride (GaN), indium gallium nitride (InGaN) or aluminum indium gallium nitride (AlInGaN), or some combination of such compounds in the active, light-emitting region. Nitride-based LEDs show a significant reduction, or “droop,” in IQE at higher injection currents.

Remarkably, the world’s smartest LED scientists are perplexed by droop behavior and vigorously strive to solve this industry-impeding puzzle. And, although researchers have recently provided various, efficiency-droop explanations, counter arguments and experiments show none are widely accepted.