Highly efficient white organic electroluminescent devices based on tandem architecture

Two types of tandem organic light-emitting diodes (OLEDs) with white-light emission have been developed by using Mg:Alq(3)/WO3 as the interconnecting layer. While the Commission Internationale d'Eclairage (CIE) coordinates of the tandem device with individual blue- and yellow-emitting OLEDs was sensitive to the viewing angle and the operating time, the tandem device connecting two white-emitting OLEDs was considerably less. At an optimal WO3 thickness of 5 nm, the tandem two-unit device produced three higher luminance efficiency than that expected of a single-unit device. A maximum efficiency of 22 cd/A was achieved by the tandem device comprised of two white-fluorescent OLEDs, and the projected half-life under the initial luminance of 100 cd/m(2) was over 80 000 h.