Synthesis and characterization of carbazolo[2,1-: a] carbazole in thin film and single crystal field-effect transistors

The synthesis of a hexacyclic fused polyheteroaromatic system, namely carbazolo[2,1-a]carbazole, via a simple two-step route is reported. Additionally, the characterization of its electronic structure is described, corresponding to a very stable molecule that is also transparent to visible light. Solid state packing is determined by X-ray diffraction analysis which, in combination with the computational calculation of the charge transfer parameters, reveals an adequate molecular arrangement to achieve a low anisotropic environment for charge transport. This π-conjugated system is used as an organic semiconductor for the fabrication of thin film and single crystal organic field-effect transistors (OFETs). Furthermore, the evaluation of different gate dielectrics results in transistors with very good hole mobilities and low operating voltages. In agreement with these results, carbazolo[2,1-a]carbazole becomes one of the best organic semiconductors belonging to the family of carbazole-based azaphenacenes.