Communication: Efficient and stable organic light-emitting devices (OLEDs) can be fabricated using hole transporting materials with a high glass transition temperature (T-g), as reported here. A series of devices utilizing high T-g hole transporting layers, consisting of compounds with a biphenyl backbone such as the one shown in the Figure, are investigated with respect to their I-V characteristics, external quantum efficiencies, ionization potentials, and electron affinities.