Scalable Ultrahigh-Speed Fabrication of Uniform Polycrystalline Thin Films for Organic Transistors

The fabrication of organic semiconductor thin films by printing technologies is expected to enable the low-cost production of devices such as flexible display drivers, RF-ID tags, and various chemical/biological sensors. However, large-scale high-speed fabrication of uniform semiconductor thin films with adequate electrical properties for these devices remains a big challenge. Herein, we demonstrate an ultrafast and scalable fabrication of uniform polycrystalline thin films with 100% surface coverage using liquid crystalline semiconductors such as 2-phenyl-7-decyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) and 2.7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8), at a rate of 3 orders of magnitude higher than before, i.e., 40 mm/s (2.4 m/min) or more by dip-coating in the drainage regime. Organic transistors fabricated with polycrystalline thin films of Ph-BTBT-10 show average mobilities of 4.13 ± 0.75 cm²/(V s) in the bottom-gate-bottom-contact configuration and 10.90 ± 2.40 cm²/(V s) in the bottom-gate-top-contact configuration comparable to those of the devices prepared with single-crystalline thin films. More importantly, these films almost maintain the FET performance when the substrate size is extended up to 4 square inch. The present findings are available for other liquid crystalline semiconductors and bring us one step closer to the realization of printed electronics.