Effect of rubrene on characteristic of red organic electroluminescent device doped with rubrene

Red organic electroluminescent device based on Alq3 doped with DCM and rubrene is fabricated. N,N′-bis-(1-naphthl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) is used as the hole-transporting layer, tris(8-quinolinolato) aluminum (Alq3) doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) and 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) as the emitting layer, and undoped Alq3 as the electron-transporting layer. We examine the dominant transfer mechanism from rubrene to DCM by comparing between the PL and EL spectrum. When the doping concentration of rubrene (6%) is similar to that of DCM (4%), red emission is improved in terms of spectral purity in comparison with that of other doped devices.