OLEDs take on the lighting market
OLEDs are starting to look like serious contenders to incumbent lighting and display technology in a week where German researchers revealed an efficient RGB-based white emitter and Samsung showed a vibrant 5in. phone display.
“For the first time, an OLED not only is able to achieve a light yield of over 60 lm/W, but also at the same time meet the international Energy Star SSL Standard with regard to colour requirements,” said German materials company BASF which is partnering with Osram.
Sheet-form OLED emitters are touted as a future replacement for fluorescent office and retail lighting – once efficiency, colour rendering, and lifetime are high enough.
To meet Energy Star, BASF has used a combination of red, green and blue emitters.
“The OLEDs contain phosphorescent metal complexes as emitter materials and customised complementary materials, which ensure optimum constancy of the colour temperatures,” said BASF. “That means the diodes are very colour-stable even when there are variations in luminous intensity.”
Lifetime is still an issue, particularly with the blue emitter.
“Our aim is to develop stable blue phosphorescence emitters. Whilst the colour coordinates and efficiencies of the new blue OLEDs are already outstanding, the service life still presents many challenges,” said Dr Elmar Kessenich, project manager at BASF. “If we manage to produce deep-blue stable emitters, that will open up the way for us to make white OLED light tiles with a light yield of more than 100 lm/W.”
BASF and Osram are working within the German government-funded OPAL (OLEDs for Applications on the Lighting Market) project, which also includes Philips.
“The challenge now lies with process engineers to apply these high efficiencies economically to large active areas,” said OPAL coordinator Dr Karsten Heuser.
Over in the Far East, Samsung last month revealed stunning-looking 125mm folding active matrix OLED display at FPD International in Japan.
The few details available at the show were that the WQVGA (480xRGBx272) display: is 0.5mm thick, has 8bit colour with better than NTSC gamut, can produce 200Cd/m sq, and will last for 20,000 hours – with life credited to “thin film encapsulation”.
If this display has plastic substrates, as opposed to two glass substrates folding together this is an exceptional lifetime. The firm also has non-folding, slightly flexible colour OLED displays.