Abstract

Since the development of the first white organic light-emitting device (OLED) in 1993, twenty years have passed. The power efficiency and lifetime of this white OLED were reportedly only <1 lm W−1 and <1 day, respectively. However, recent rapid advances in material chemistry have enabled the use of white OLEDs for general lighting. In 2012, white OLED panel efficiency has reached 90 lm W−1 at 1000 cd m−2, and a tandem white OLED panel has realized a lifetime of over 100 000 hours. What is more important in OLEDs is to shed clear light on the new design products, such as transparent lighting panels and luminescent wallpapers. These fascinating features enable OLEDs as a whole new invention of artificial lighting. In this review, we would like to overview the recent developments of white OLED, especially three key elemental technologies related to material chemistry: (1) low operating voltage technology, (2) phosphorescent OLED technology and (3) multi-photon emission (MPE) device technology.