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 (CDM) 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-hydroxyquinolin 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.