The solvent effect on the morphology and molecular ordering of benzothiadiazole-based small molecule for inkjet-printed thin-film transistors

A small molecule organic semiconductor, D(D′–A–D′)(2) comprising benzothiadiazole as an acceptor, 3-hexylthiophene, and thiophene as donors, was successfully synthesized. X-ray diffraction and atomic force microscopy were used to investigate the effect of a dual solvent system with varying ratios of chloroform and toluene on film crystallinity and film morphology via inkjet printing. The film prepared with a chloroform to toluene ratio of 1.5 : 1 showed better performance with improved crystallinity and morphology due to having enough time to control the arrangement of molecules. In addition, by optimizing ratios of CHCl(3) to toluene, the inkjet-printed TFT based on 3HTBTT using a CHCl(3) and toluene ratio of 1.5 : 1 was successfully fabricated and exhibited a hole mobility of 0.01 cm(2) V(−1) s(−1) due to the improved molecular ordering of the 3HTBTT film.