Optimization of thieno[2,3-b]thiophene derivatives for air-stable organic field-effect transistors

In this research, four novel thieno[2,3-b]thiophene (TT) derivatives incorporating triple bonds were developed and investigated as active layers for organic field-effect transistors (OFETs). The compounds were investigated through thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV-visible spectroscopy (UV-vis), and cyclic voltammetry (CV) to assess thermal, optical, and electrochemical characteristics. All TT-based semiconductor thin films, fabricated using the solution-shearing technique, demonstrated p-channel activity. Notably, both compound 2 ([2,5-bis(phenylethynyl)thieno[2,3-b]thiophene], with a benzene ring linked to the TT core via a triple bond) and compound 4 ([2,5-bis(thiophen-2-ylethynyl)thieno[2,3-b]thiophene], with a thiophene ring similarly connected) demonstrated superior electrical characteristics in ambient with carrier mobility up to similar to 0.075 cm(2)/Vs with a current on/off ratio >10(6). The surface morphology and microstructure of the semiconductor thin films were analyzed through theta-2 theta X-ray diffraction (XRD) and atomic force microscopy (AFM). The results revealed that the absence of steric hindrance caused by methyl groups contributed to higher crystallinity and improved film texture, which correlated with enhanced device performance. Furthermore, the devices maintained consistent performance even after 90 days of storage, demonstrating superior air stability.