Solution processable organic thin-film transistors (OTFTs) have attracted great attention recently due to their high potentials to dramatically reduce the manufacturing cost for large-area and flexible electronic devices. However, most high performance polymeric semiconductors require chlorinated solvents for their device fabrications, which is not an environmentally friendly manufacturing process. In this article, we describe a facile approach to tuning the solubility characteristics of a high mobility polythiophene system by strategic structure modification and demonstrate significantly improved solution properties in environmentally benign solvents with high field-effect mobility up to 0.18 cm(2) V-1 s(-1). To our best knowledge, this is one of the highest mobility values reported so far for solution-processed OTFTs fabricated from polymeric semiconductors in nonchlorinated solvents. Furthermore, the molecular orientations and structural properties of newly developed polythiophenes were evaluated by both single crystal data of their building blocks and X-ray diffraction (XRD) of their thin films.