New fluorene-based bipolar charge transporting materials

Air-stable and solution-processable fluorene-based bipolar charge transporting materials (CTMs) were designed, synthesized, and analyzed. These CTMs feature anthraquinone, 9-fluorenone, and 9-dicyanofluorenylidine groups and exhibit good film formation properties for solvent processing. Quantum chemistry simulations and optical absorption measurements proved that several stable conformers and charge transfer complexes form inside the molecules. Hole mobilities in CTMs were around 10^-4 to 10^-5 cm² V^-1 s^-1, while electron mobility in compounds with anthraquinone and 9-dicyanofluorenylidine groups was approximately one order of magnitude lower.