High efficient white organic light-emitting diodes based on triplet multiple quantum well structure

We demonstrate the high efficient triplet multiple quantum well (MQW) structure white organic light-emitting diodes (WOLEDs) (MQW-WOLEDs) by introducing phosphorescent Ir-complex material. In the triplet MQW-WOLEDs, 1,3,5-tris(N-phenyl-benzimidazol-2-yl)benzene functions as the potential barrier layer; fluorescent dopant layer and Ir-complex phosphorescent dopant layer act as the blue-emitting and orange-emitting potential well layer, respectively. The maximum luminance, current efficiency, and power efficiency are 19 000 cd/m2, 14.5 cd/A, and 5.4 lm/W, respectively; and the efficiency roll-off is especially improved by ∼15% over reference device. The emission spectra almost do not change with the changing drive voltage; that is, Commission Internationale de I’Eclairage coordinates x and y vary only ±0.002 and ±0.008 from 8 to 14 V. The improvement of electroluminescence performances is attributed to the balanced electron-hole injection and transport, confinement of carriers and excitions within potential well; as well more detail of improvement mechanism is discussed.