Synthesis and characterization of soluble indolo[3,2-b]carbazole derivatives for organic field-effect transistors

The synthesis and characterization of new soluble materials based on the indolo[3,2-b]carbazole (IC) framework is presented. These new molecules are particularly suitable for p-channel organic field-effect transistors (OFETs) because of the high level of crystallinity usually found in IC derivatives. To obtain soluble materials, the synthesis of new 2- or 3-bromoindolo[3,2-b]carbazole backbone was performed which allowed the synthesis of molecule bearing the IC moieties on both ends. Either Suzuki cross-coupling or Horner–Emmons reaction were used as the final step. Thin films of these new materials, along with 3,9-diphenyl-5,11-dioctylindolo[3,2-b]carbazole (3POIND), a material previously reported, were obtained by using different processing techniques. Polarized optical microscopy (POM) and X-ray diffraction (XRD) experiments on these solution-processed films showed high crystallinity. Transistors fabricated with these thin films gave a hole mobility as high as 0.06 cm2 V−1 s−1 with drop-cast films and 0.12 cm2 V−1 s−1 when the films were processed with the shearing technique.