Researchers at Princeton University (Princeton, NJ) and the University of Southern California (Los Angeles, CA) have used a phosphorescent sensitizer to excite a fluorescent dye and nearly quadruple the efficiency of a fluorescent red organic light-emitting device (OLED). The new design replaces the simple emissive layer in a conventional OLED with a complex layer composed of alternating phosphorescent and fluorescent materials. In the conventional design, only excitons with singlet spin configuration go on to emit light while wasting the energy of excitons with triplet spin configuration and yielding an efficiency of about 25%. The complex layer quadruples the efficiency of the device by enabling light emissions from excitons with triplet spin configuration also.
Stephen Forrest, head of the research team, which is also collaborating with Universal Display Corp. (Ewing, NJ), said the new technique would be available to electronics manufacturers within six months for applications such as car stereo displays. He added that it might eventually lead to widespread use of OLEDs in Palm Pilots, cell phones, and laptop computers with substantially increased energy efficiency. Contact Stephen Forrest at [email protected].