Charge Carrier Mobilities in Amorphous Triphenylamine--Fluorene Copolymers: Role of Triphenylamine Unit in Intra- and Intermolecular Charge Transport

We investigated the effect of the triphenylamine (TPA) content of TPA--fluorene copolymers on their charge carrier mobilities. Intramolecular mobilities were measured by flash-photolysis time-resolved microwave conductivity (TRMC), while intermolecular hole mobilities were determined on the basis of space-charge limited current (SCLC) and field-effect transistor (FET). TRMC and SCLC except for FET showed an analogous dependence on the TPA content. The results are discussed from the viewpoints of delocalization of singly-occupied molecular orbital of radical cation, conformation of polymer chain, and trap effect. This study highlights the importance of optimizing the TPA content in the polyfluorene backbone for electronic device application.