A study on the phosphorescent blue organic light-emitting diodes using triplet exciton blocking layer.

We studied the use of N,N'-dicarbazolyl-3,5-benzene (mCP) of the triplet energy level 2.90 eV and p-bis(triphenylsilyly)benzene (UGH2) of the wide triplet energy band gap 3.50 eV as triplet exciton blocking layer (TEBL) to get high efficiency in phosphorescent blue organic light-emitting diodes. Five devices (Devices I-V) with different structures were fabricated to investigate the effect of mCP and UGH2 TEBLs on device performances. The maximum quantum efficiencies of devices I, II, III, IV and V were 5.10%, 1.41%, 5.90%, 4.98% and 0.61%, respectively.