Efficient multilayer (ML) and single layer (SL) phosphorescent organic light-emitting devices (PHOLEDs) with a bipolar host 9,9′-[4′-(2-ethyl-1H-benzimidazol-1-yl) [1,1′-biphenyl]-3,5-diyl] bis-H-Carbazole (EBBPC) are fabricated. The photophysical, electrochemical and carrier transporting properties of EBBPC host are investigated. The maximum external quantum efficiency (EQE) can reach 14.9%, 15.6%, 16.0% and 15.4% for red (R), green (G), blue (B), and white ML-PHOLEDs, respectively. And the maximum EQE can also reach 10.1%, 14.6% and 9.8% for R, G, and B SL-PHOLEDs, respectively. Besides, the SL-PHOLEDs show low efficiency roll-off due to the broader exciton formation zone in SL OLEDs. The excellent performance of ML- and SL-PHOLEDs could be attributed to the balanced bipolar transporting properties and appropriate energy level of the host.

具有双极性主体9,9'-[4'-（2-乙基-1 H-苯并咪唑-1-基）的高效多层（ML）和单层（SL）磷光有机发光器件（PHOLED），[1， 1'-联苯基] -3,5-二基]双-H-咔唑（EBBPC）被制造。研究了EBBPC宿主的光物理，电化学和载流子传输特性。红色（R），绿色（G），蓝色（B）和白色ML-PHOLED的最大外部量子效率（EQE）分别可以达到14.9％，15.6％，16.0％和15.4％。R，G和B SL-PHOLED的最大EQE也可以分别达到10.1％，14.6％和9.8％。此外，由于SL OLED中激子形成区域较宽，因此SL-PHOLED的滚降效率较低。ML和SL-PHOLED的出色性能可归因于平衡的双极传输特性和适当的主体能级。