A new coumarin derivative used as emitting layer in organic light-emitting diodes

The photoluminescence and electroluminescence properties of a new coumarin derivative N-(7-diethylamino-coumarin-3-carboxyl)-N,N′-dicyclohexylurea (DCDU) were investigated. The compound showed a maximum quantum efficiency of 0.943 for 400 nm excitation. The cleavage of intramolecular hydrogen bond led to conformational transition of coumarin derivative during vacuum deposition, and the deposited film was formed with less crystalline phase. A stable yellow light emitted from a triple-layer EL device with a maximum brightness of 1100 cd/m2 and an external efficiency of 0.4%.