Monday, 28 March 2011

From the OSRAM laboratory: efficiency record for warm white

 Peak values right on the Planckian curve

OSRAM Opto Semiconductors has set a brand spanking new laboratory record of 142 lm/W for the efficiency of a warm white LED light source. With a correlated color temperature (CCT) of 2755 K the LED achieves a nice color rendering index (CRI) of 81. Measurements were taken under standard conditions: room temperature and pulsed mode at an operating current density of 350 mA/mm².

Bright warm white light with high efficiency is important for lighting applications in the residential sector. The laboratory setup for a warm white LED shows the gigantic potential of these energy-saving semiconductor light sources: The peak value of 142 lm/W measured under standard conditions is achieved at a color perception that closely matches that of a classic incandescent lamp (color coordinates cx 0.46/ cy 0.41 on the Planckian curve).

The laboratory setup for a warm white LED achieves a peak value of 142 lm/W directly on the Planckian curve at 2700 K; an optimized setup at 3000 K could accomplish 160 lm/W.

If they explore this technical approach further and permit deviations from the Planckian curve they ought to even now be able to accomplish higher efficiency values of up to 160 lm/W for a correlated color temperature of 3000 K (cx 0.45/ cy 0.44), said Dr. Norwin von Malm, Predevelopment Manager at OSRAM Opto Semiconductors. If they apply this approach to a 2 mm² chip they can improve efficiency by an additional 10 to 15 percent for the same operating current. They would then expect 180 lm/W for a pure warm white LED and nice color rendering.

The increase in efficiency was made feasible by combining new procedures in thin-film and UX:3 chip technologies and in conversion. Development engineers at OSRAM Opto Semiconductors have benefited here from combined know-how in all aspects of the production method. These include epitaxial growth, thin-film chip architectures, conversion processes and package technologies.
OSRAM is part of the Industry sector of Siemens and one of the two leading lighting manufacturers in the world. Its subsidiary, OSRAM Opto Semiconductors GmbH in Regensburg (Germany), offers its customers solutions based on semiconductor technology for lighting, sensor and visualization applications. OSRAM Opto Semiconductors has production sites in Regensburg (Germany) and Penang (Malaysia). Its headquarters for North America is in Sunnyvale (USA), and for Asia in Hong Kong. OSRAM Opto Semiconductors also has sales offices throughout the world. For more information go to

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