Enhanced efficiency of blue phosphorescent organic light-emitting diode base on triple-emitting layer with mixed host system.

We report an improvement of efficiency in blue phosphorescent organic light-emitting diodes (PHOLEDs) based on triple-emitting layer (T-EML) with mixed host (MH) system using a phosphorescent blue emitter: iridium(III)bis[(4,6-di-fluoropheny)-pyridinato-N,C2]picolinate (Flrpic) doped in N,N'-dicarbazolyl-3,5-benzene (mCP) of hole transport-type host material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) of electron transport-type host material. This T-EML device resulted in both an effective electron and hole balance and efficient distribution of the recombination zone. As a result, the property of T-EML device which demonstrated a maximum luminous efficiency of 24.45 cd/A and a external quantum efficiency of 10.9%. It also showed a high maximum power efficiency of 13.82 lm/W, which is approximately two times higher than that of the control device.