The electron-accepting [1,2,4]triazolo[1,5-a]pyridine (TP) moiety was introduced to build bipolar host materials for the first time, and two host materials based on this TP acceptor and carbazole donor, namely, 9,9′-(2-([1,2,4]triazolo[1,5-a]pyridin-2-yl)-1,3-phenylene)bis(9H-carbazole) (o-CzTP) and 9,9′-(5-([1,2,4]triazolo[1,5-a]pyridin-2-yl)-1,3-phenylene)bis(9H-carbazole) (m-CzTP), were designed and synthesized. These two TP-based host materials possess a high triplet energy (>2.9 eV) and appropriate highest occupied molecular orbital/lowest unoccupied molecular orbital levels as well as the bipolar transporting feature, which permits their applicability as universal host materials in multicolor phosphorescent organic light-emitting devices (PhOLEDs). Blue, green, and red PhOLEDs based on o-CzTP and m-CzTP with the same device configuration all show high efficiencies and low efficiency roll-off. The devices hosted by o-CzTP exhibit maximum external quantum efficiencies (η ext ) of 27.1, 25.0, and 15.8% for blue, green, and red light emitting, respectively, which are comparable with the best electroluminescene performance reported for FIrpic-based blue, Ir(ppy) 3 -based green, and Ir(pq) 2 (acac)-based red PhOLEDs equipped with a single-component host. The white PhOLEDs based on the o-CzTP host and three lumophors containing red, green, and blue emitting layers were fabricated with the same device structure, which exhibit a maximum current efficiency and η c of 40.4 cd/A and 17.8%, respectively, with the color rendering index value of 75.
- high efficiency
- high triplet energy
- phosphorescent organic light-emitting diodes (PhOLEDs)
- universal host materials
- white organic light-emitting diode
ASJC Scopus subject areas
- Materials Science(all)