Pure-Red Dye for Organic Electroluminescent Devices: Bis-Condensed DCM Derivatives

In this paper, the bis-condensed 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran (DCM) derivatives are introduced as a new class of red dye for organic light-emitting devices (OLEDs). They showed more red-shifted emission than the mono-substituted DCM derivatives and the emission maxima increased as the electron-donating ability of the aromatic donor group increased. On the basis of these results, red light-emitting devices were fabricated with bis-condensed DCM derivatives as red dopants. For a device of configuration ITO/TPD/Alq3 + DADB (5.2 wt.-%)/Alq3/Al (where ITO is indium tin oxide, TPD is N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, Alq3 is tris(8-hydroxyquinoline) aluminum, and DADB is [2,6-bis[2-[5-(dibutylamino)phenyl]vinyl]-4H-pyran-4-ylidene]propanedinitrile), pure red emission was observed with Commission Internationale de l'Eclairage (CIE 1931) coordinates of (0.658, 0.337) at 25 mA/cm2.