Water‐Surface Drag Coating: A New Route Toward High‐Quality Conjugated Small‐Molecule Thin Films with Enhanced Charge Transport Properties

Abstract

Electronic properties of organic semiconductor (OSC) thin films are largely determined by their morphologies and crystallinities. However, solution‐processed conjugated small‐molecule OSC thin films usually exhibit abundant grain boundaries and impure grain orientations because of complex fluid dynamics during solution coating. Here, a novel methodology, water‐surface drag coating, is demonstrated to fabricate high‐quality OSC thin films with greatly enhanced charge transport properties. This method utilizes the water surface to alter the evaporation dynamics of solution to enlarge the grain size, and a unique drag‐coating process to achieve the unidirectional growth of organic crystals. Using 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl)anthradithiophene (Dif‐TES‐ADT) as an example, thin films with millimeter‐sized single‐crystal domains and pure crystallographic orientations are achieved, revealing a significant enhancement (4.7 times) of carrier mobility. More importantly, the resulting film can be directly transferred onto any desired flexible substrates, and flexible transistors based on the Dif‐TES‐ADT thin films show a mobility as high as 16.1 cm2 V−1 s−1, which represents the highest mobility value for the flexible transistors reported thus far. The method is general for the growth of various high‐quality OSC thin films, thus opening up opportunities for high‐performance organic flexible electronics.

Scalable Growth of Organic Single‐Crystal Films via an Orientation Filter Funnel for High‐Performance Transistors with Excellent Uniformity

“…This behavior has been commonly observed in solution-printed organic small-molecule thin films. [20][21][22][23][24][25][26] As expected, the C 8 -BTBT crystal domains of the film in the CGR also exhibit a uniform color (Figure 2a, bottom), indicating the single-crystalline nature of the film. High-magnification POM image reveals that the C 8 -BTBT OSCF is composed of long, highly aligned ribbon-shaped crystal domains (Figure 2b, left).…”

“…Among them, MGC has shown great promise to attain aligned and millimeter-wide organic single-crystalline domains due to its compatibility with continuous high-throughput manufacturing techniques. [22][23][24][25][26] Despite these successful progresses, controlled growth of the crystal array with unitary crystallographic axis is still in its fancy. A central challenge is that stochastic nucleation often causes seed crystals with diverse orientations that will induce the subsequent crystal growth in disordered orientations.…”

A Fully Solution‐Printed Photosynaptic Transistor Array with Ultralow Energy Consumption for Artificial‐Vision Neural Networks

“…We chose Dif-TES-ADT as a model semiconductor material because of its large photoresponse, excellent electrical properties, and high crystallinity. [23,24] Additionally, previous works have disclosed the existence of a number of electron traps within the bandgap of p-type solution-processed Dif-TES-ADT, [26,27] enabling the trapping and detrapping of photogenerated carriers to achieve photosynaptic functionalities. To obtain excellent charge transport characteristics, we adopted blade coating for the fabrication of OSC thin films, because it makes use of a unidirectional force to guide the oriented growth of grains in OSC thin films.…”

Structures, Properties, and Device Applications for [1]Benzothieno[3,2‐b]Benzothiophene Derivatives

“…Furthermore, external force could be used to assist the self‐assembly of organic materials. [ 117,118 ] Wang et al used external force to grow 2D C10‐BTBT single crystals on water surface. [ 119 ] Moreover, Deng et al.…”