Solution-processable dendric triphenylamine nonamers as hole-transporting and hole-injection materials for organic light-emitting devices

We demonstrated two solution-processable triphenylamine dendric nonamers: the N-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.