Uniaxially oriented polycrystalline thin films and air-stable n-type transistors based on donor-acceptor semiconductor (diC8BTBT)(FnTCNQ) [n=0, 2, 4]

We report the fabrication of high quality thin films for semiconducting organic donor-acceptor charge-transfer (CT) compounds, (diC(8)BTBT)(F(n)TCNQ) (diC(8)BTBT = 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene and F(n)TCNQ [n = 0,2,4] = fluorinated derivatives of 7,7,8, 8,-tetracyanoquinodimethane), which have a high degree of layered crystallinity. Single-phase and uniaxially oriented polycrystalline thin films of the compounds were obtained by co- evaporation of the component donor and acceptor molecules. Organic thin- film transistors (OTFTs) fabricated with the compound films exhibited n-type field- effect characteristics, showing a mobility of 6.9 x 10(-2) cm(2)/V s, an on/off ratio of 10(6), a sub-threshold swing of 0.8 V/dec, and an excellent stability in air. We discuss the suitability of strong intermolecular donor-acceptor interaction and the narrow CT gap nature in compounds for stable n-type OTFT operation. (C) 2015 AIP Publishing LLC.