1,3,4-Oxadiazole Containing Silanes as Novel Hosts for Blue Phosphorescent Organic Light Emitting Diodes

Five rigid oxadiazole (OXD) containing silanes, denoted 1–5, have been developed with high morphological stability. Disruption of the π-aromatic conjugation by introduction of Si atoms leads to a large band gap and high triplet energy. Among the OXDs we studied, 2,5-bis(triphenylsilylphenyl)-1,3,4-oxadiazole 5 is the best host for FIrpic, with a phosphorescent organic light emitting diode (PHOLED) turn-on voltage of 6.9 V, maximum luminance of 5124 cd/m2, current efficiency of 39.9 cd/A, and external quantum efficiency of 13.1%. Special molecular stacking in the single crystal of 5 was discussed.