Pentacene thin film transistors fabricated by solution process with directional crystal growth

We have fabricated solution-processed pentacene thin film transistor arrays with mobilities as high as 1.0 cm²/V s, evaluated at a low drain voltage of ?10 V. This is achieved by controlling the growth direction of the pentacene films from solution, and by optimizing conditions for drop casting. Crystal growth of the solution-processed pentacene films is found to proceed in one direction on a tilted substrate. Grazing incidence X-ray diffraction and electron diffraction reveal that the crystal growth azimuth corresponds to the direction along the minor axis of the a–b plane in the unit cell of the pentacene crystal. This directional growth method is extended to solution processing on large glass substrates with an area of 150 × 150 mm², thereby yielding transistor arrays with two-dimensional uniformity and high carrier mobility.