Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors.

We developed a facile method for fabricating large-area, two-dimensional (2D), organic, highly crystalline films and extended it to organic thin-film transistor arrays. Tilted spinning provided oriented flow at the three-phase contact line, and a 2D crystalline film that consisted of layer-by-layer stacked 2,7-diocty[1]benzothieno[3,2- b]benzothiophene (C8-BTBT) was obtained facilely for organic thin-film transistors (OTFTs). The extracted field-effect mobility is 4.6 cm2 V-1 s-1, but with nonideal features. By applying this method to microdroplet arrays, an oriented crystal was fabricated, and the channel region for OTFTs was covered by adjusting the spinning speed. By tuning the tilt angle (θ) of the revolving substrate, we fabricated high-performance OTFT arrays with average and maximum mobilities of 7.5 and 10.1 cm2 V-1 s-1, respectively, which exhibited high reliability factors of over 90% and were close to that of ideal transistors. These results suggest that high-quality crystalline films can be obtained via a facile tilted-spinning method.