Osram Opto chips narrow green gap
Osram Opto Semiconductors is bringing 180 lm 1 mm2 green-emitting chips for LED backlight units to market, saying that the devices are unmatched by its competitors.
Green emitters are lagging behind red and blue chips in terms of brightness, hampering efforts to make bright RGB sources that combine the three, a “green gap” problem the German company now says it is now very close to solving.
Osram s laboratory devices produce light at 527 nm using a refined version of its InGaN-on-sapphire ThinGaN technology, with the highest brightness of 180 lm produced at 1 A.
In comparison, the company's existing generation of chips would only produce 100 lm at this current. The new chips can deliver 100 lm at 350 mA.
Meanwhile, with its InGaAlP technology, Osram has demonstrated 615 nm 1 mm2 red chips that can reach 300 lm at 2 A.
The red chips are highly efficient, producing 52 lm/W, in comparison to Osram's best commercially available red LED, which claims a luminous efficacy of 38 lm/W.
“We have achieved this enormous increase in brightness above all by designing the new chips to handle higher currents,” said Ralph Wirth, a development engineer at Osram Opto. “This has resulted from optimizing the series resistors.”
Aimed for use in single chip and multichip LEDs, the green devices will also find use in backlighting, while the red devices have been developed primarily for projection applications.
Both new chips are expected to enter volume production in summer 2008.
