Recent progress and current challenges in phosphorescent white organic light-emitting diodes (WOLEDs)

White organic light-emitting diodes (WOLEDs) offer a promising avenue to developing future energy-saving solid-state lighting sources because of their intrinsic characters such as low driving voltages, high brightness and efficiency, large area, etc. While commercialization of WOLEDs has attracted tremendous interest in both academic and industrial communities, the discovery of highly efficient phosphors opens up a good channel to meet this target. With the goal towards practical application, many design strategies, including new materials synthesis, judicious design of device configuration, wise management of charges/excitons in different active layers, development of sophisticated and low cost fabrication procedures, etc. have been put forward to achieve high efficiency, good white color stability and quality. In this review, the most recent progress and achievements in various research aspects of the phosphorescent WOLED is presented. Practical applications are enumerated and illustrated by specific examples. The major advances, ongoing challenges and future perspectives of this research frontier are also critically discussed. The present work provides valuable clues to the specialists in the field to develop new routes for future research development of WOLEDs.