Blue organic light-emitting diodes based on $Mes2B$ [$p-4,4′$-biphenyl-NPh(1-naphthyl)]

Here, we report highly efficient blue organic light-emitting diodes (OLEDs) with $Mes2B$ [$p-4,4′$-biphenyl-NPh(1-naphthyl)] (BNPB) as a blue emitter. It is found that both efficiencies and electroluminescent color are very sensitive to the selection of electron transport materials in the devices. For an optimized structure [indium tin oxide/2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane $(1nm)∕N,N′$-di(naphthalen-1-yl)-$N,N′$-diphenyl-benzidine $(45nm)$/BNPB $(20nm)$/1,3,5-tris(2-$N$-phenylbenzimidazolyl) benzene $(30nm)$/LiF $(1nm)$/Al] with BNPB as an undoped blue emitter, a maximum current efficiency can reach $3.5cd∕A$⁠. It is found that BNPB emits two distinct peaks, one of around $450nm$ and the other of $485nm$⁠, and their respective emission intensities depend on the nature of majority charge carrier in the emission layer.