On‐Top π‐Stacking of Quasiplanar Molecules in Hole‐Transporting Materials: Inducing Anisotropic Carrier Mobility in Amorphous Films

Abstract Dimers of partially oxygen‐bridged triarylamines were designed and synthesized as hole‐transporting materials. X‐ray structural analyses revealed that these compounds form on‐top π‐stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the π‐stacking. Surprisingly, even in vacuum‐deposited amorphous films, these compounds retained some of the face‐on π‐stacking, thus facilitating an out‐of‐plane carrier mobility.