New benzothieno[3,2-b]benzothiophene (BTBT)-based soluble semiconducting molecules have been synthesized through Horner-Emmons coupling reactions using 5-alkylthiophene-2-carbaldehyde and BTBT-diethylphosphonate. The only difference between the two molecules is the length of alkyl chains as a substituent. The molecules are intrinsically thermotropic liquid crystalline (LC) and exhibit good solubility in common organic solvents. The semiconducting properties of the two LC molecules were evaluated in organic thin film transistors (OTFTs). After annealing the samples at the temperature at which liquid crystallinity appears, the TFT device performance improved significantly. The two conjugated molecules 4 and 5 exhibited fairly high charge carrier mobilities of 0.020 cm 2/(Vs) (Vth = -14.5 V, ION/OFF = 1.42 × 105) and 0.023 cm2/(Vs) (Vth = -2.0 V, I ON/OFF = 1.20 × 106), respectively.
Bibliographical noteFunding Information:
This research work was supported by 21st century Frontier Research Program ( F0004091-0000-00 ). Particularly, D.H. Choi acknowledges the financial support by the Seoul R&BD Program ( 10543; 2009-2010 ). X-ray experiments at PLS were supported by the Ministry of Science and Technology and Pohang Steel Company. This research was supported by Korea Science and Engineering, (KOSEF R0120070001128402008 ).
- Conjugated molecule
- Liquid crystallinity
- Organic semiconductor
- Thin film transistor
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Chemistry
- Electrical and Electronic Engineering