Tetsuzo Miki

Bipyridyl oxadiazoles as efficient and durable electron-transporting and hole-blocking molecular materials

We have demonstrated new and efficient electron transporting (ET) and hole blocking (HB) materials for organic light-emitting devices (OLEDs). The bipyridyl-substituted oxadiazole derivatives can form a stable glassy state with glass transition temperatures greater than 100 °C. The bipyridyl-substituted oxadiazole derivatives have excellent ET, HB and electron accepting ability and also exhibit electrical operation durability. Bipyridyl-substituted oxadiazoles are a promising candidate for ET and HB materials for OLEDs.

P-165: Wet-Processable Triphenylamine Dendrimers as Hole-Transporting and Hole-Injection Materials for Organic Light-Emitting Devices

We demonstrated two wet-processable triphenylamine dendric nonamers: the nitrogen-atom-centered nonamer (TPA9-1) and the phenyl-centered nonamer (TPA9-2). The materials were found to have high glass transition temperature (Tg) up to almost 200°C. The fractional difference of the central units of the molecular structures caused different adaptability due to the different ionization potentials (Ip). TPA9-1 (N-atom-centered), whose Ip was smaller than that of TPA9-2 (phenyl-centered), was suitable as hole injection layer material, and TPA9-2 was suitable as hole-transporting layer material. Computational chemistry provides a ready explanation for the Ip difference between the two materials.

5.3: New Triazole Derivatives as Hole‐Blocking and Electron‐Transporting Materials for Organic Light‐Emitting Devices

We have demonstrated bipyridyl substituted triazole derivatives (Bpy-TAZs) as an electron-transporting material for organic light-emitting devices (OLEDs). Hybridization of bipyridyl to triazole is a good way to improve electron-transporting ability of triazoles with keeping good hole-blocking ability, which is a useful property of triazole derivatives. By employing a new Bpy-TAZ (Bpy-TAZ-03) as a hole-blocking and electron-transporting material for phosphorescent OLEDs, lower operation voltage was achieved with keeping the same external quantum efficiency of electroluminescence (almost 10%) as compared with the conventional hole-blocking and electron-transporting bilayer consisting of bathocuproine and tris (8-hydroxyquinolinato) aluminum.