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 of 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 cm2 Vs�1 (25 cm2 Vs�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
