With partial funding from the U.S. Department of Energy, Lumileds, a lighting company that develops, manufactures, and distributes LEDs and related products, has developed a high-power LED emitter with increased efficacy to improve luminaire performance in directional lighting applications. The efficacy improvement achieved by Lumileds' LED emitter will result in more direct energy savings, while reducing initial and lifecycle cost at a luminaire level and enabling LED conversion of the most demanding applications.
High-power LEDs are particularly suitable for directional applications (e.g., security lights, spot lights), as they are optimized for high-drive-current and high-temperature operation with a small source size and a well-defined radiation profile. The developed technology elements in Lumileds' emitter will be implemented in future upgrades of Lumileds’ LUXEON V, a 4 mm2 patterned sapphire substrate flip-chip (PSS-FC) high-power LED, as well as other PSS-FC-based products.
The improving efficacy of LED lighting is driving LED conversion across a wide range of lighting applications. State-of-the-art, high-power white LEDs have an efficacy that ranges between 130 lumens per Watt (lm/W) (warm-white) to 160 lm/W (cool-white) under typical operating conditions. Significant further improvements up to 225-250 lm/W are thought to be possible but are difficult to achieve, as many of the individual components are already approaching their practical limits. Realizing maximum efficacy gains requires an approach that investigates and takes into consideration the interactions between the elements inside the LED device.
Lumileds' LED emitter demonstrated an efficacy of 181 lm/W under normalized conditions at a correlated color temperature (CCT) of 4000K and a color rendering index (CRI) of about 70, which is a 23% gain over the baseline of 147 lm/W at the beginning of the project. This efficacy gain was realized by an integrated development effort with improvements in each of the abovementioned LED technology elements.