Abstract

Three derivatives of 2-anilino-5-phenylpenta-2,4-dienenitrile, i.e.1–3, were assessed as the emitting materials in organic electroluminescent devices. A single hetero-junction device was fabricated using 2 (or 3) as the emitter, which was doped 3% by weight into 1,1′,1″-triphenyl-2,2′,2″-(benzene-1,3,5-triyl)tri-1H-benzimidazole (TPBI). It can be turned on at voltage 6 V, with luminance up to ∼6000 Cd m⁻² (∼2000 Cd m⁻² for 3) and an external quantum efficiency ∼0.75% (0.25% for 3). The performance was improved considerably by inserting an additional layer of 4,4′-dicarbazolyl-1,1′-biphenyl (CBP) between the hole-transporting layer and TPBI. A more than doubled luminance and external quantum efficiency were obtained for the revised configuration. In another design, the emitting layer was constructed by spin-coating a mixture of 1 doped into polycarbazolylethylene (PVK). The device could be turned on at 12 V and reached a luminance of 650 Cd m⁻² at 22 V. The physical properties of these compounds as well as the devices' characteristics were discussed.