A novel D-π-A blue fluorophore based on [1,2,4]triazolo[1,5-a]pyridine as electron acceptor and its application in organic light-emitting diodes

[1,2,4]triazolo[1,5-a]pyridine (TP) is employed as a novel electron acceptor to construct a deep-blue bipolar fluorescent emitter (TPP-PPI) for the first time. Single crystals of TPP-PPI show a special packing mode which may provide a carrier transport channel. TPP-PPI has a high photoluminescence quantum yield of 97.5% in neat film. Non-doped organic light emitting diodes (OLEDs) with the new compound as emitter exhibits a high-performance deep-blue emission with an external quantum efficiency (EQE) of 6.05% and CIE coordinates of (0.15, 0.11) at 1000 cd m^-2. The doped devices based on TPP-PPI shows comparable performances and better deep-blue color purities. A 20 wt% TPP-PPI based OLED displays an EQE_max of 6.34% and a color index of (0.15, 0.06), satisfying European Broadcasting Union blue color standard. Furthermore, the high triplet energy (2.33 eV) allows TPP-PPI to be used as a host for PO-01 phosphor to realize high performance range phosphorescent OLED (EQE_max = 24.7%).