OLEDs are based on organic (carbon-based) materials. Unlike LEDs, which are small point sources, OLEDs are made in sheets that provide a diffuse-area light source. While developing rapidly, OLED technology is less mature than LED technology, whose rapid advancement has created a moving target for OLED products in terms of lighting performance and pricing. Still, OLED manufacturers are optimistic that with a few key breakthroughs, OLEDs will offer a value proposition complementary with LED lighting approaches. Innovations are still needed on multiple fronts to increase the efficiency, lifetime, and light output of OLED devices. The development of device architectures and materials systems (particularly blue) that allow for improved stability and efficiency, and methods to extract the light generated by the OLED, remain key challenges.