Shaanxi Key Laboratory of Photonics Technology for Information, Department of Electronic Science and Technology, School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049
Abstract：A phosphorescent organic light emitting diode by using tetrafluorotetracyanoquinodimethane (FTCNQ) as the indium-tin-oxide modification layer and 4,4'-bis(carbazol-9-yl)biphenyl (CBP) as the hole transporting layer is reported. CBP doped with a green phosphorescent dopant, tris(2-(p-tolyl)pyridine) iridium(III) (Ir(mppy)3) is used as the emission layer in this device, and the maximum current efficiency of 31.3 cd/A is achieved. Furthermore, low efficiency roll-off of 10.4% is observed with device luminance increasing from 100 cd/m2 (29.7 cd/A) to 10000 cd/m2 (26.5 cd/A). It is demonstrated that a charge-generation area is formed at F4TCNQ/CBP interface, which will benefit hole injection into the hole transporting layer. Moreover, use of the CBP hole transporting layer will benefit the low efficiency roll-off by broadening triplet exciton formation, as well as by avoiding accumulation of unbalanced carrier at the hole transporting layer/emission layer interface.
2014, Vol. 31 
