Osram jumps at ‘green gap’

The ‘green gap’ – the lack of efficient semiconductor materials that produce green light – has been the target of research at many organisations.

osram-led-green-gap

Osram Opto is the latest to have a go, using indium gallium nitride (InGaN)-based green LEDs.

It claims to have reduced typical forward voltages by around 600mV and increased optical output power at the same time, claiming improvements in efficiency of up to 40% compared to predecessor products in its UX:3 portfolio.

Forward drop is now 2.6V at 45A/cm2 current density.

“The crucial factors in increasing efficiency were improved charge carrier transport and optimised material quality in the epitaxial layers,” said the firm. “The benefits are considerable, particularly for applications in which red, blue and green LEDs are used in combination, because all three colours now have a voltage of less than 3V the drivers, which were previously designed for higher maximum voltages, can now be dimensioned smaller.”

At 350mA, 1mm2 UX:3 chips are now achieving 175lm/W, and more at wavelengths around 530nm.

Absolute light output exceeds 300 lm at 1A.

“Until recently, these efficiency values seemed unattainable for green direct emitting InGaN LEDs. We are now moving into areas that up to now have been achievable only with phosphor conversion emitters but with significantly reduced spectral quality,” said Osram project manager Adam Bauer.

The research that produced these improvements has revealed potential for even more efficiency, said the firm, and its team is working on this.


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