Novel benzo[b]thieno[2,3-d]thiophene derivatives with an additional alkyl-thiophene core: synthesis, characterization, and p-type thin film transistor performance

Abstract

In this paper, three novel organic materials based on the benzo[b]thieno[2,3-d]thiophene (BTT) core structure with an additional alkyl-thiophene core and end-capping alkyl side chains were synthesized and characterized. Furthermore, we explored the potential use of these compounds as solution-processed organic semiconductors (OSCs) for organic thin film transistors (OTFTs). Thermal, optical, and electrochemical properties of three organic compounds were investigated for elucidating the physicochemical information of each compound. Then, the solution-shearing (SS) method was employed to form thin films of the compounds due to its merit with regard to molecular packing and thin film crystallinity, and microstructure as well as crystallinity of the thin films were investigated with θ–2θ X-ray diffraction (XRD) and atomic force microscopy (AFM). All fabricated OTFTs exhibited p-channel activity under ambient conditions, and especially transistors based on the BTT core structure with a branched alkyl chain featured hole mobility up to 0.057 cm² V⁻¹ s⁻¹ (V_{DS =} −100 V) and current on/off ratio exceeding 10⁷, in accordance with thin films of the corresponding compound showing superb surface coverage and high film texture.