OSRAM Opto Semiconductors and BASF have developed a highly efficient white organic light-emitting diode (OLED). This is for the first time that an OLED not only is able to achieve a light yield of more than 60 lm/W, but also meets the international Energy Star SSL Standard with regard to color requirements.
 
Although this efficiency benchmark had previously been achieved, until now the color values of OLEDs have not been within the acceptable band for color coordinates around the Planck curve, as defined by the Energy Star SSL Standard. The color values of the new OLED are within this band its light retains the white color at different levels of intensity.

By developing a white OLED with a high light yield, the two companies have completed a major step on the way toward commercial OLED lighting. In the development laboratories, highly efficient semiconductor materials from BASF Research were combined with standard materials and thereby new standards set with regard to color coordinates and efficiency. BASF and OSRAM are conducting research together within the framework of the OLEDs for Applications on the Lighting Marke (OPAL) project. The OPAL project is being sponsored as part of the OLED Initiative of the German Federal Ministry for Education and Research (BMBF). Within the framework of the OPAL project, the experts at BASF are dealing with the material side of the OLEDs and, are developing the optimum component structures in partnership with Philips and OSRAM.

The new OLEDs contain phosphorescent metal complexes as emitter materials and customized complementary materials, which ensure optimum constancy of the color temperatures. That means that, owing to the use of new materials, the diodes are very color-stable even when there are variations in luminous intensity. The challenge now is to optimize the life of these OLED tiles, especially by stabilizing the blue emitters.

Beyond luminous efficiency, OLEDs offer even more convincing advantages. The laboratory results show that the new OLEDs are five times as efficient as filament bulbs and up to 50 percent more efficient compared with standard low-energy lamps. OLEDs consume much less electricity than conventional sources of light, so consumers in the future will be able to cut their electricity costs with OLEDs.

Dr. Elmar K, OLED project manager at BASF Future Business GmbH, noted BASF reached an important milestone in OLED research a few years ago. White OLEDs can best be obtained by combining red, green and blue light. For a long time, there was no efficient source for deep-blue light. In 2003, BASF researchers laid the foundation for a phosphorescent blue emitter by developing a new class of materials based on an iridium complex. Their aim is to develop stable blue phosphorescence emitters. While the color coordinates and efficiencies of the new blue OLEDs are already outstanding, the service life still presents many challenges explains If they manage to produce deep-blue stable emitters, that will open up the way for them to make white OLED light tiles with a light yield of more than 100 lm/W

According to Dr. Karsten Heuser, OPAL Coordinator and Director OLED Lighting Technology at OSRAM Opto Semiconductors, in the future, OLED will be suitable for general lighting as flat sources of light for offices or as decorative lighting in stores. And they not only offer the potential of being considerably more economical, but are also capable of being used in a variety of ways as flat, transparent and, eventually, flexible sources of light. They will provide completely new opportunities in terms of design and performance in part owing to newly developed semiconductor materials from BASF. The challenge now lies with the process engineers to apply these high efficiencies economically to large active areas.