An iodine effect in ambipolar organic field-effect transistors based on indigo derivatives†
5,5′-Diiodoindigo (4) exhibits excellent ambipolar transistor properties with hole/electron mobilities of μh/μe = 0.42/0.85 cm2 V−1 s−1. The halogen substituted indigos show decreasing tilt angles from F to I in the crystals. In addition, the iodine–iodine interaction provides extraordinarily large interchain interaction. However, the X-ray diffraction suggests that the indigo molecules are arranged approximately perpendicular to the substrate in the thin films, probably due to the extra iodine–iodine interaction. The remarkable performance is ascribed to this characteristic supramolecular interaction.