Solution‐printed organic single‐crystalline films hold great potential for achieving low‐cost manufacturing of large‐area and flexible electronics. For practical applications, organic field‐effect transistor arrays must exhibit high performance and small device‐to‐device variation. However, scalable fabrication of highly aligned organic crystalline arrays is rather difficult due to the lack of control over the crystallographic orientation, crystal uniformity, and thickness. Here, a facile solution‐printing method to fabricate centimeter‐sized highly aligned organic crystalline arrays with a thickness of a few molecular layers is reported. In this study, the solution shearing technique is used to produce large‐area, organic highly crystalline thin films. Water‐soluble ink is printed on the hydrophobic surface of organic crystalline films, to selectively protect it, followed by etching. It is shown that the addition of a surfactant dramatically changes the fluid drying dynamics and increases the contact line friction of the aqueous solution to the underlying nonwetting organic crystalline film. As a result, centimeter‐scale highly aligned organic crystalline arrays are successfully prepared on different substrates. The devices based on organic crystalline arrays show good performance and uniformity. This study demonstrates that solution printing is close to industrial application and also expands its applicability to various printed flexible electronics.

printing methods on various desirable substrates. Many soluble small-molecule organic semiconductors with high carrier mobility have been developed over the past decade, such as [1] benzothieno [3,2-b] benzothiophene (BTBT) derivatives. [11] The higher field-effect mobility of smallmolecule organic semiconductor (OSC) thin films is achieved with crystallization and crystal orientations, which are optimized for charge conduction. [12] Thus, state-of-the-art solution-processable OSCs have demonstrated excellent characteristics with better carrier mobility surpassing those of solution-processed metal oxides and amorphous silicon thin film transistors. [13,14] However, because of the vigorous crystallization of small-molecule organic semiconductors during the solvent evaporation, the polycrystalline domains with uncontrollable orientations and sizes are frequently developed, which results in a notably nonuniform film morphology. Hence, devices with high mobility and device-to-device uniformity are difficult to fabricate. Various solution based methods have been developed to control the thin film crystallization, [15] such as solution shearing, [16] inkjet printing, [17] slot-die coating, [18] spray printing, [19] and screen printing. [20] Among these methods, screen printing is considered a simple, efficient, and low-cost method to fabricate electronic devices in industry. The printing process for one layer consumes only few seconds, which is efficient for the mass production of organic electronics. Previous studies on screen-printed electronics mainly focused on the printing of conducting materials and inorganic semiconductors using high viscosity ink. [21,22] Thus, the thickness of the printed film often relies on the thickness of emulsion of the screen, which is commonly up to few micrometers. Obviously, screen printing is not suitable for depositing OSC thin films of OFET because of the huge contact resistance caused by the micrometer-scale film thickness. Although some works have fabricated screen-printed OFET devices based on polymer OSCs, [23] the device performance (mobility ≈ 0.03 cm 2 V −1 s −1 ) is inadequate for various applications. Therefore, the development of a simple and low-cost printing approach that can directly fabricate highly Control over the morphology and crystallinity of small-molecule organic semiconductor (OSC) films is of key importance to enable high-performance organic optoelectronic devices. However, such control remains particularly challenging for solution-processed OSC devices because of the complex crystallization kinetics of small-molecule OSC materials in the dynamic flow of inks. Here, a simple yet effective channel-restricted screen-printing method is reported, which uses small-molecule OSCs/insulating polymer to yield largegrained small-molecule OSC thin-film arrays with good crystallization and preferred orientation. The use of cross-linked organic polymer banks produces a confinement effect to trigger the outward convective flow at two sides of the channel by the fast solv...