High performance pure blue organic fluorescent electroluminescent devices by utilizing a traditional electron transport material as the emitter
Abstract
In this work, we demonstrated a novel device design strategy to obtain efficient pure blue organic fluorescent electroluminescent (EL) devices by doping a traditional electron transport material, 9,10-bis[4-(6-methylbenzothiazol-2-yl)phenyl]anthracene (DBzA), into a hole transporting host material, 4,4′,4′′-tris(carbazol-9-yl)-triphenylamine (TcTa), as the light-emitting layer (EML). Here, DBzA functions not only as a blue emitter but also as an electron transport material. Due to the well matched energy levels of DBzA and TcTa, the obtained devices displayed a broadened recombination zone, improved trapping of carriers, and balanced distribution of holes and electrons on emitter molecules. Interestingly, a single-EML device displayed higher EL efficiencies and lower operation voltage than those of a double-EML device. Finally, a pure blue EL device (Commission Internationale de l'Eclairage (CIE) coordinates of (0.141, 0.165)) with maximum brightness, current efficiency, power efficiency and external quantum efficiency (EQE) of up to 10 384 cd m−2, 6.41 cd A−1, 6.71 lm W−1, and 4.3%, respectively, was realized by optimizing the doping concentration. Even at a certain brightness of 1000 cd m−2, current efficiency as high as 4.1 cd A−1 (EQE = 2.8%) can be retained by the same device.