Osram boosts luminous efficacy of high power LEDs
Osram Opto Semiconductors has 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 processes.
At a current density of 3 A/mm2 the quantum efficiency of the LEDs is now a full 7.5 percent 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 InGaN 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 therefore achieve a significant increase in the efficiency of the LEDs. Under laboratory conditions and at a current density of 3 A/mm2 a typical luminous flux of 740 lm was verified in a QFN LED package - an improvement of around 7.5 percent compared with previous typical values (6200 K, Cx 0.319, Cy 0.323, single-chip version LDxyz).
At low current densities of 0.35 A/mm2 the benefit of the optimised LEDs is still around 4 percent. "We have been able to reduce the droop effect considerably by extensively revising and improving the epitaxy", said Alexander Frey, project manager at the Regensburg company.
The new 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 now be integrated step by step in the existing product portfolio.
