Dithieno-naphthalimide based copolymers for air-stable field effect transistors: synthesis, characterization and device performance

Abstract

A new thiophene-fused naphthalimide building block, 9-(2-decyltetradecyl)-8H-dithieno-[3′,2′:3,4; 2′′,3′′:5,6]benzo[1,2-f]isoindole-8,10(9H)-dione (4), was synthesized and three novel conjugated copolymers P1–P3 based on this building block and electron-rich units such as 4,4′-didodecyl-2,2′-bithiophene (for P1), benzo[1,2-b:4,5-b′]dithiophene (for P2) and 3,6-didodecylthieno[3,2-b]thiophene (for P3) were prepared by Stille coupling polymerization. The optical, electrochemical and thermal properties of polymers P1–P3 were studied and their applications in organic field effect transistors (OFETs) were also investigated. These new polymers have good solubility in common organic solvents and exhibit good thermal stability. Polymers P1 and P3 entered nematic liquid crystalline phases above 213 and 313 °C, respectively. The average field-effect hole mobilities were evaluated to be 0.15, 3 × 10⁻³ and 0.05 cm² V⁻¹ s⁻¹ for P1, P2 and P3, respectively, under ambient conditions, with a high on/off ratios of 10⁵–10⁷. All the OFETs based on these polymers showed good environmental stability when stored in air.