euroLED conference report
must approve – “[today] it is quite a mess and not consistent.”
Other factors also come into play, which depend on the target application. For example, for the lighting of outdoor areas, van den Berg said that the payback associated with LED deployment is too long, and must reduce to less than three years through improvement in the cost per lumen and chip efficiency. Warmer colour temperatures that are stable for decades are also needed.
Another sector, office light, is a “tough market” to penetrate, according van den Berg. He pointed out that the T5 fluorescent is a very cheap incumbent with an efficacy comparable to that of the best LEDs of today. To have success here, makers of LED lighting must convince owners of offices to re- consider their approach to lighting this space by looking at lux levels. If they think along these lines, they may switch to greater use of task lighting and to lower ambient lighting, changes that may lead to increased LED deployment.
To enable LEDs to penetrate these areas and also replace conventional bulbs in the lighting of shops, van den Berg believes that the cost per lumen must fall by 95 percent. Delivering this massive hike in affordability will require improvements to recombination, extraction and phosphor conversion efficiencies, plus higher drive current densities, superior package designs, higher chip yields, greater fab utilization and the availability of better production tools.
When Pollock spoke, he echoed many of the points made by van den Berg. But he also ventured into new territory, showing the audience how far the LED community had progressed in recent years: between 2006 and 2011, the efficacy of industry-leading cool-white LED products driven at their maximum drive current increased from 50 lm/W to 90 lm/W, and the cost per lumen fell by more than an order of magnitude. Pollock also detailed the improvement to the quality of Cree’s LR6 downlight over a similar timeframe. Back in 2007,
Putting these figures in perspective, Ohno explained that blue LEDs with yellow phosphors are capable of 294 lm/W, and sources that employ colour mixing of red, green and blue devices could just top 400 lm/W. The quality of the colour rendering provided by such schemes depends on the width of the sources. During fifty years of refinement of the fluorescent lamp, broadband sources have been replaced by narrowband equivalents to improve colour rendering, and Ohno expects the same shift to occur in the LED industry.
this high-quality white-light source that blends the emission of white LEDs with red-emitting variants employed 42 devices consuming a total of 12 W to deliver 650 lumens. Last year, the same light output was realized with 8 LEDs consuming 10.5 W, and this product was far more affordable – it had fallen from a commercial wholesale price of more than $100 in 2007 to a retail price tag of just $50.
Failings of the CRI metric Issues relating to categorizing the quality of light were highlighted in a presentation from Yoshi Ohno from the National Institute of Standards and Technology. He began his talk by explaining that colour quality was governed by both the chromaticity of the light source and colour rendering, which is a measure of how the colours of an object are reproduced under this illumination. He then gave clear examples of how two sources with the same CRI could make objects appear to have very different colours.
For years and years, makers of LEDs have been trying to increase the efficacy of their LED chips. The theoretical maximum for any lighting source is 683 lm/W, but that is for a green source of a particular wavelength; a low-pressure sodium lamp could hit 520 lm/W, but the colour rendering of this source is poor.
Although the presentations of Ohno and many of the other speakers showed that there is still much work to do for the LED lighting industry, the general mood is that this technology is certain to lead a lighting revolution. Many exhibitors highlighted the breadth of LED lighting products that are available today, and this industry is set to thrive as it makes improvements to colour quality and efficacy, alongside lower prices.
Resources
General Electric’s video promoting LEDs can be found at:
www.youtube.com/ watch?v=Dlbl21vyZbY)
The world market for lamps and luminaires in general & exterior lighting, 2011 edition by IMS Research
© 2011 Angel Business Communications. Permission required.
The leading LED
chipmakers According to IMS research, the leading manufacturers for LEDs in 2010, in terms of revenue, were:
Nichia
Samsung Osram
Seoul Semiconductor Cree
Philips Lumileds LG Innotek Everlight
15 percent 10 percent 9 percent 8 percent 6 percent 5 percent 4 percent 4 percent
July 2011
www.compoundsemiconductor.net 27
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