Efficient yellow–green light-emitting cationic iridium complexes based on 1,10-phenanthroline derivatives containing oxadiazole-triphenylamine unit

• Yellow–green light-emitting cationic iridium complex with 1,10-phenanthroline derivative containing triphenylamine-oxadiazole.
• Thermally stable and high glass-transition temperature up to 240 °C.
• The luminance efficiency of 30.6 cd/A and an external quantum efficiency of 10.2%.

Cationic iridium(III) complexes with 1,10-phenanthroline (phen) derivatives containing oxadiazole-triphenylamine, oxadiazole or triphenylamine unit used as neutral auxiliary ligands, with the formula of [Ir(ppy)2(op-phen)][PF6] (C1), [Ir(ppy)2(o-phen)][PF6] (C2), and [Ir(ppy)2(p-phen)][PF6] (C3) (ppy = 2-phenylpyridine) were synthesized, respectively. The complexes exhibit high thermal stability and were used as phosphorescent dopants in polymer light-emitting diodes (PLEDs) with the configuration of ITO/PEDOT: PSS/PVK (70): PBD (30): complex (x, wt.%)/TPBI/CsF/Al. The complexes C1, C2 and C3 exhibit high electroluminescent performances with the maximum luminance efficiencies of 30.6 cd/A, 28.4 cd/A and 26.3 cd/A, respectively. The Commission Internationale de L'Eclairage (CIE) color coordinates of all complexes are (0.41, 0.55) corresponding to the yellow-green region. The complex C1 containing bipolar unit of oxadiazole-triphenylamine exhibits higher efficiency due to its balance of hole and electron fluxes.

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