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

The photoluminescence and electroluminescence properties of a new coumarin derivative N-(7-diethylamino-coumarin-3-carboxyl)-N,N'-dicyclohexylurea (DC DU) were investigated. The compound showed a maximum quantum efficiency of 0.943 for 400 nm excitation. The cleavage of intramolecular hydrogen bond l ed to conformational transition of coumarin derivative during vacuum deposi tion, and the deposited film was formed with less crystalline phase. A stab le yellow light emitted from a triple-layer EL device with a maximum bright ness of 1100 cd/m(2) and an external efficiency of 0.4%. (C) 1999 Elsevier Science S.A. All rights reserved.