Fabrication of Wafer-Scale Organic Single-Crystal Films with Uniform In-Plane Orientation via Wetting-Assisted In-Air Sublimation for High-Performance Transistor Arrays

The production of single-crystalline organic thin films on a large scale is challenging but imperative for industrial applications of organic electrics. This work improves a vapor-based method on the basis of our recently invented microspacing in-air sublimation (MAS) to achieve wafer-scale uniform single-crystalline organic films. The method alters the wettability of both the bottom and top substrates in MAS. By virtue of the vapor-to-melt-to-crystal process and the unique genetic relationship between the morphology of source materials and that of the grown crystals, wettability control on the one hand promotes the dispersion of the molten source materials and on the other hand drives the liquid crystal phase on the top substrate to form uniform single-crystalline films over the whole substrate. Using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) as an example, centimeter-sized crystalline films with pure orientations are achieved. Transistor arrays fabricated on the crystalline films exhibit high yield and uniform performance with an average mobility of 3.91 cm2 V–1 s–1. This method provides an opportunity to realize vapor-grown single-crystalline films but not random and discrete single crystals via physical vapor transport nor the amorphous/polycrystalline films via vacuum deposition, which may be a step toward future commercialization of organic electronics.