High Performance OTFTs Fabricated Using a Calamitic Liquid Crystalline Material of 2‐(4‐Dodecyl phenyl)[1]benzothieno[3,2‐<i>b</i>][1]benzothiophene

Abstract

An air‐stable calamitic liquid crystalline material, 2‐(4‐dodecyl phenyl)[1]benzothieno[3,2‐ b ]benzothiophene (C12‐Ph‐BTBT), is designed with a highly ordered smectic X (SmX) (X = K or H) phase demonstrating high charge‐carrier mobility and thermal stability in thin‐film transistors. Organic thin‐film transistors show mobilities as high as 8.7 cm 2 V −1 s −1 when the C12‐Ph‐BTBT thin film is annealed at its SmX phase before the electrode deposition. Structural characterization reveals that the as‐deposited C12‐Ph‐BTBT thin films adopt a unilamellar structure. On the other hand, after polycrystalline thin films of C12‐Ph‐BTBT exhibit bilayer structure after annealing at the temperature of the SmX and the smectic E phases. The highest charge‐carrier mobility is observed when the C12‐Ph‐BTBT thin films are annealed at the SmX phase before the electrode deposition. The results give insight into the understanding of the nature of the mesophase behavior of liquid‐crystalline semiconductors and can aid the rational design of self‐organizing molecular semiconductors.