With the ongoing challenge to develop more highly efficient brilliant light sources than are currently available, Philips Lighting, Philips Research, and Novaled report that they have set a new record in the efficiency of high-brightness OLEDs.
By combining Philips and Novaled technology and research, a 25-lumens-per-watt power efficiency has been achieved in a white-emitting OLED, with a brightness level of 1000 candelas per meter.
According to Dr. Dietrich Bertram, manager, OLED development for Philips Lighting, even though 'OLEDs suffer from many loss channels, so far limiting their efficiency to values much below the theoretical possible efficiency,' the trick is the right combination of materials and the position of the materials in the layer stack that makes up the OLED device; thus, the potential for OLEDs to generate light is very good.
Core differences between LEDs and OLEDs include the make-up of the lighting device and the light created. LEDs are based on little crystals, grown on a wafer, while OLEDs are thin layers typically placed on conducting glass. LEDs generate a lot of light out of a tiny volume and are quasi point-like sources, while the brightness of OLEDs is typically much lower, but distributed over a larger area, creating a more diffuse light source that enables the combination of shapes and color.
While they have already pushed the limits of OLED technology, Philips' chief technology officer, Klaas Vegter, is confident that 'this is not the end of the development and that OLEDs will establish themselves as the second solid-state lighting technology in the market.'
Results from research and development will be used in ongoing projects and in the recently started European project OLLA (Organic LEDs for Lighting Applications). A similar project has been established in the United States, an initiative by the Department of Energy on inorganic and organic LED lighting, called NGLI (Next Generation Lighting Initiative). Find out more at www.netl.doe.gov.ssl/.