Turning blue is good news for solid-state lighting

摘要

Scientists have been trying to get an organic compound that emits a stable blue light with a lifetime that exceeds the previously thought 1000 hr lifetime barrier ever since Shuji Nakamura's invention of the first inorganic blue LED in the mid-90s. The challenge with stability for blue emission, however, is that it requires a very high energy, and many failure mechanisms exist that make obtaining long-term reliability a daunting challenge, says Janice Mahon, VP of technology commercialization at Universal Display Corp. (UDC). UDC's recent announcement of a longer operating-lifetime phosphorescent-organic LED (PHOLED), > 15,000 hr at 200candela/ m~2, was achieved with a deeper blue (at 474nm peak emission wavelength) as defined by CIE coordinates (0.16, 0.37). (CIE is a color mapping system first developed by the Commis- sion Internationale de l'Eclairage.) The external quantum efficiency was reported to be 9.5% with a 22cd/amp luminous efficiency.