Osram Advances Work on OLEDs
Osram Opto Semiconductors Inc. of San Jose, Calif., has announced progress on its white organic light-emitting diode (OLED) project. The project, funded by a $4.65 million grant from the US Department of Energy, was initiated in 2004 to research the potential of white OLEDs as an energy-saving product for commercial and residential lighting.
The company has achieved a 25-lm/W polymer OLED. The cool-white-emitting diode uses a solution-processable, phosphorescent, blue-emitting device in conjunction with an external inorganic phosphor layer. This 14 lm/W of blue color was achieved by embedding an efficient phosphorescent blue emitter in a polymer host.
The company has also demonstrated a 20-lm/W phosphorescent device based on a white-emitting polymer blend. This diode employs no external phosphors, and the white emission comes directly from the phosphorescent polymer. The company hopes to use the advances as a basis to develop large-area light tiles.
The polymer OLED enables color tuning, using a design based on three separate, printable polymer inks emitting in the red, green and blue portions of the spectrum. Ink-jet was used to pattern the small, three-color segments. The product’s driver circuitry enables users to regulate color from dark blue to white. The technology offers large-size scalability without losses in optical and electrical properties.