A novel deep-blue emitter PhImPOTD based on phenathroimidazole was synthesized, which is incorporated by an electron-donating dibenzothiophene unit and electron-withdrawing phenanthroimidazole and diphenylphosphine oxide moieties. Furthermore, the weak π-π stacking and intermolecular aggregation render the photoluminescence quantum yield is as high as 0.34 in the solid state. Non-doped organic light emitting diodes (OLEDs) based on PhImPOTD emitter exhibits a low turn-on voltage of 3.6 V, a favorable efficiency of 1.13 cd A-1 and a deep blue emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.08). The CIE is very close to the NTSC (National Television Standards Committe) blue standard (CIE: 0.14, 0.08). PhImPOTD is also utilized as blue emitter and the host for a yellow emitter (PO-01) to fabricate white organic light-emitting diodes (WOLEDs). This gives a forward-viewing maximum CE of 4.83 cd A-1 and CIE coordinates of (0.32, 0.32) at the luminance of 1000 cd m-2. Moreover, the single-carrier devices unambiguously demonstrate that typical bipolar-dominant characteristics of PhImPOTD. This work demonstrates not only that the phenanthroimidazole unit is an excellent building block to construct deep blue emission materials, but also the introduction of a diphenylphosphine oxide deprotonation substituent is an efficient tactic for harvesting deep-blue emitting devices.
Keywords: Bipolar; Doped white; Non-doped deep blue; OLEDs; Phenanthroimidazole derivative.