High Recombination Efficiency White OLEDs

Lighting is estimated to consume 8.2 quads (approximately 762 TWh), or about 22% of the total electricity generated in the U.S. New, high efficiency solid state light sources, such as light emitting diodes (LEDS) and organic LEDs (OLEDS), are needed to reduce the ever increasing demand for energy. An OLED is potentially a cost-effective diffuse light source that may compete most directly with conventional incandescent light sources; however, improvements in the overall efficiency of these devices are still required before they become commercially viable and attain expected cost and performance goals (of $3 per 1000 lumens and 90 lumens per watt, respectively). This project will utilize novel OLED fabrication techniques to enable 40 lm/W, organic, solid-state lighting sources to replace 12 lm/W incandescent sources, and hence reduce overall energy consumption in the U.S. In Phase I, the stated efficiency goal was surpassed: OLED architectures were designed and materials were incorporated to enable the creation of a warm white phosphorescent OLED, which had an efficacy of 36 lm/W at a luminance of 1,000 cd/m2, a correlated color temperature of 4,400 K, and a color rendering index of 71. In addition, it was shown that the device can be operated continuously at constant current for over 200 hrs before its initial luminance of 1,550 cd/m2 decreases to 775 cd/m2. In Phase II, the power efficiency and operational stability of the phosphorescent OLED will be enhanced via improvements in the recombination efficiency of electrons and holes in the OLED emissive layer. Because the recombination efficiency is directly affected by the doping of emissive molecules into a host material, precise control of the mixture of dopants and host molecules will be implemented by using an organic vapor phase deposition technology. Commercial Applications and other Benefits as described by the awardee: Today, OLED technology is the leading emerging technology for flat panel displays (FPDs). Many features desired for FPDs also are making OLED technology of great interest for solid-state lighting: (1) OLEDs are bright and colorful lambertian emitters with excellent power efficiency at low voltages; (2) they are thin-film devices that provide thin form factors especially when built on flexible plastic substrates; and (3) they require less materials, have fewer processing steps, and may be less capital intensive than today¿s dominant liquid crystal displays. If high-recombination-efficiency materials were added to the mix, the technology should become cost-effective in general lighting applications