Patent ID: 7638207

Claim:
An organic electroluminescent device, comprising: a) a substrate; b) an anode and a cathode; c) a light-emitting layer disposed between the anode and cathode including a host and a light-emitting dopant according to formula M1; wherein: A and A′ represent independent azine ring systems corresponding to 6-membered aromatic ring systems containing at least one nitrogen; (X a ) n and (X b ) m represent one or more independently selected substituents and include acyclic substituents or we joined to form a ring fused to A or A′; m and n are independently (I) to 4; Z a and Z b are independently selected substituents; 1,2,3,4,1′,2′,3′,4′ are independently selected as either carbon or nitrogen atoms; and provided that X a , X b , Z a and Z b , 1,2,3,4,1′,2′,3′,4′ are selected to provide blue luminescence; and d) a hole-transporting structure disposed between the light-emitting layer and the anode including three sublayers, a first sublayer in contact with the light-emitting layer and including a first hole-transporting material and a first stabilizing dopant which is an anthracene, and a second sublayer in contact with the first sublayer including a second hole-transporting material and a second stabilizing dopant which is an anthracene, and a third dopant having a bandgap that is smaller than each of the bandgaps of the second hole-transporting material and the second stabilizing dopant, respectively and the third sublayer including a hole-transporting material disposed between the second sublayer and the anode.