Temperature dependences of electroluminescent characteristics in the devices fabricated with novel triphenylamine derivatives

In this paper, we investigated the temperature dependences of the electroluminescent (EL) characteristics of two-layer devices fabricated using four hole-transporting materials based on triphenylamine, and a typical emitting material, tris (8-quinolinolato) aluminum. The thermal stability of the organic EL devices is clearly seen to depend on the glass transition temperature (T_g) of the hole-transporting material. The EL device with a pentamer of triphenylamine exhibits uniform light emission in a continuous operation up to 155°C without breakdown. A lowering of the “turn-on voltage” for light emission and an increase of luminous efficiency with increasing temperature are found in the devices. Excellent durability of continuous operation is also achieved at high temperatures. Our results indicate that the linear linkage of triphenylamine provides the high T_g material and the high device performance at high temperatures