Organic semiconductors with higher carrier mobility and better transparency have been actively pursued for numerous applications, such as flat-panel display backplane and sensor arrays. The carrier mobility is an important figure of merit and is sensitively influenced by the crystallinity and the molecular arrangement in a crystal lattice. Here we describe the growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from a blended solution

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... f C8-BTBT and polystyrene by using a novel offcentre spin-coating method. Combined with a vertical phase separation of the blend, the highly aligned, meta-stable C8-BTBT films provide a significantly increased thin film transistor hole mobility up to 43 cm 2 Vs À 1 (25 cm 2 Vs À 1 on average), which is the highest value reported to date for all organic molecules. The resulting transistors show high transparency of 490% over the visible spectrum, indicating their potential for transparent, high-performance organic electronics.