High Performance Exciplex-Based Fluorescence-Phosphorescence White Organic Light-Emitting Device with Highly Simplified Structure

Exciplex systems have become increasingly important due to their good performance in devices. Considering their bipolar transporting properties, exciplex systems with strong blue fluorescence and high triplet energies could potentially be ideal hosts for fluorescence phosphorescence hybrid (F-P) white organic light-emitting diodes (WOLEDs). Here we achieved an efficient blue exciplex system formed with a new material (4-dimesitylboryl)phenyltriphenylamine (TPAPB) and 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi), which exhibited a high photoluminescence quantum yield of 44.1%. Using only these two organic materials, a high performance blue-emitting OLED was fabricated with a maximum external quantum efficiency (EQE) of 7.0 +/- 0.4%. Such high efficiency is not only among the highest results of blue fluorescent organic light-emitting diodes (OLEDs) but also indicates that high chi (fraction of excitons that can potentially radiatively decay) can be as well achieved via a TTA triplet up-conversion process. By simply doping an orange phosphor, the first F-P WOLED using an exciplex host system was realized with a single-emission-layer structure and merely three organic materials. The WOLED exhibits a maximum power efficiency, current efficiency, and EQE of 29.6 +/- 0.2 lm W-1, 42.5 +/- 0.3 cd A(-1), and 15.7 +/- 0.3%, respectively. To the best of our knowledge, this highly efficient and structurally simplified exciplex-based F-P WOLED is truly unprecedented.