Meta-substituted bipolar imidazole based emitter for efficient non-doped deep blue organic light emitting devices with a high electroluminescence

Enormous endeavors have been made to explore pure and efficient deep-blue electroluminescent materials for organic light emitting devices (OLEDs). However, materials with deep-blue emission and high efficiencies for non-doped OLED devices are still limited. In view of this, a novel ambipolar meta-substituted emitter (TPA-BIPI) is synthesized by combining phenanthroimidazole, benzimidazole and triphenyl-amine units for OLED devices. Non-doped OLED device is constructed by employing TPA-BIPI as emitter which gives deep-blue emission at 442 rim with CIE of (0.149, 0.105). The EQE of the device is obtained to be as high as 4.53% with the current efficiency (CE) of 4.3 cd/A and a power efficiency (PE) of 3.71m/W. A low driven voltage of 3.4 V, a reduced efficiency roll-off and a high electroluminescence of 12,491 cd/m(-2) is also achieved. This combination of donor and acceptor moieties indicates a strong potential to prepare efficient bipolar materials for OLEDs.