Osram increases efficacy of high-power LEDs

13th April 2016

Jordan Mulcare

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Osram Opto Semiconductors’ research lab has considerably improved the luminous efficacy of its high-power LEDs by reducing the unwanted droop effect at high currents. This development was made possible by optimised epitaxial growth processes. At a current density of 3A/mm², the quantum efficiency of the LEDs is now a full 7.5% above the previous level.

The unwanted drop in efficiency as the current density increases, commonly referred to as 'droop', limits the maximum luminous efficacy of indium gallium nitride based LEDs and is, therefore, the subject of intense research and development activities worldwide. Engineers at Osram Opto Semiconductors have now been able to reduce this effect considerably and achieve a significant increase in the efficiency of the LEDs.

Under laboratory conditions and at a current density of 3A/mm², a typical luminous flux of 740lm was verified in a QFN LED package (Quad Flat No Lead) – an improvement of around 7.5% compared with previous typical values (6200K, Cx 0.319, Cy 0.323, single-chip version). Even at low current densities of 0.35A/mm², the benefit of the optimised LEDs is still around 4%. “We have been able to reduce the droop effect considerably by extensively revising and improving the epitaxy," said Dr. Alexander Frey, Project Manager at the Regensburg company.

The processes are being used in all LEDs from Osram Opto Semiconductors based on UX:3 chip technology and will also have a positive impact on other high-power products. The results will be integrated step by step in the company’s existing product portfolio.