Electroluminescence of phenothiazine-labeled dendrimer encapsulated 2-{2-[2-(4-dimethylamino-phenyl)-vinyl]-6-methyl-pyran-4-ylidene}-malononitrile derivative: Effect of the density of phenothiazine dendron

Red light emitting dendrimer (3) was synthesized by reacting 2-[2,6-bis-(2-{4-[bis-(6-hydroxy-hexyl)-amino]-phenyl}-vinyl)-pyran-4-ylidene] -malononitrile (2) with 3,5-bis-{3,5-bis-[2-(10-hexyl-10H-phenothiazin-3-yl)- vinyl]-benzyloxy}-benzoic acid (i). The red emitting core dye capable of electronic excitation via Förster energy transfer was encapsulated by phenothiazine (PTZ) dendrons. The multi-layered devices showed a luminance of 210 cd/m² at 321 mA/cm² (11.7 V) for the dendrimer only and 295 cd/m² at 246 mA/cm² (11.4 V) for the dendrimer with 3 wt% of PTZ dendron. The EL quantum efficiency (η_ext = 0.79%) increased after doping an additional amount of PTZ dendron into the dendrimer.