Solution-processable n-type semiconductors based on unsymmetrical naphthalene imides: Synthesis, characterization, and applications in field-effect transistors

A series of unsymmetrical naphthalene imide derivatives (1-5) with high electron affinity was synthesized and used in n-channel organic field-effect transistors (OFETs). They have very good solubility in common organic solvents and good thermal stability up to 320 °C. Their photophysical, electrochemical, and thermal properties were investigated in detail. They showed low-lying LUMO energy levels from -3.90 to -4.15 eV owing to a strong electron-withdrawing character. Solution-processed thin-film OFETs based on 1-4 were measured in both N₂ and air. They all showed n-type FET behavior. The liquid-crystalline compounds 1 a, 1 b, and 3 showed good performance owing to the self-healing properties of the film in the liquid-crystal phase. Compound 3 has an electron mobility of up to 0.016 cm ² V^-1 s^-1 and current on/off ratios of 10 ⁴-10⁵.