Highly efficient green organic light-emitting devices based on terbium complex by employing hole block material as host

Abstract

In this work, efficient green electroluminescent (EL) devices with simplified device structure were prepared by doping trivalent terbium complex Tb(PMIP)3 into hole block material TmPyPB. The high triplet energy of TmPyPB helps to confine excitons within light-emitting layer, while the electron transport characteristic of TmPyPB facilitates the balance of carriers on Tb(PMIP)3 molecules. By optimizing the doping concentration of Tb(PMIP)3 and the thickness of each functional layer, highly efficient green EL device with the structure of ITO/MoO3 (3 nm) /TAPC (50 nm) /Tb(PMIP)3 (30 wt%):TmPyPB (25 nm) /TmPyPB (60 nm) /LiF (1 nm) /Al (100 nm) displayed pure Tb3+ characteristic emission with maximum current efficiency, power efficiency and brightness up to 47.24 cd/A (external quantum efficiency (EQE) of 14.4%), 43.63 lm/W and 1694 cd/m2, respectively. At certain brightness of 100 cd/m2, the device still maintained a current efficiency of 19.96 cd/A (EQE=6.1%). Such a device design strategy helps to improve the EL performances of Tb(PMIP)3 and to simplify device fabrication processes, thus reduce the fabrication cost.