Controlled Growth of Ultrathin Film of Organic Semiconductors by Balancing the Competitive Processes in Dip-Coating for Organic Transistors

Abstract

Ultrathin film with thickness below 15 nm of organic semiconductors provides excellent platform for some fundamental research and practical applications in the field of organic electronics. However, it is quite challenging to develop a general principle for the growth of uniform and continuous ultrathin film over large area. Dip-coating is a useful technique to prepare diverse structures of organic semiconductors, but the assembly of organic semiconductors in dip-coating is quite complicated, and there are no reports about the core rules for the growth of ultrathin film via dip-coating until now. In this work, we develop a general strategy for the growth of ultrathin film of organic semiconductor via dip-coating, which provides a relatively facile model to analyze the growth behavior. The balance between the three direct factors (nucleation rate, assembly rate, and recession rate) is the key to determine the growth of ultrathin film. Under the direction of this rule, ultrathin films of four organic semiconductors are obtained. The field-effect transistors constructed on the ultrathin film show good field-effect property. This work provides a general principle and systematic guideline to prepare ultrathin film of organic semiconductors via dip-coating, which would be highly meaningful for organic electronics as well as for the assembly of other materials via solution processes.

2D Organic Materials for Optoelectronic Applications

“…Solution‐processing methods, including solution cast‐assembly, solution epitaxy, dual solution‐shearing, and others have proved to be capable of producing high quality, large scale monolayer organic single crystal growth. Different from epitaxial growth of organic molecules on a specific substrate, organic single crystals made by these methods can be adopted to almost any kind of noncrystalline substrate even on a water surface.…”

Solution‐Processed 2D Molecular Crystals: Fabrication Techniques, Transistor Applications, and Physics

“…Considering the adjustments in molecular structures and deposition parameters, various solution‐based techniques have been extensively used to achieve precise controllable growth of 2DMCs with high morphological uniformity and perfect crystalline order. These techniques include, but are not limited to, drop‐casting, spin‐coating, dip‐coating, solution‐shearing, floating‐coffee‐ring‐driven‐assembly, pen writing, etc. In the following sections, we highlight these exemplary methods reported in the literatures ( Table 1 ).…”

“…The unit of x , y ‐axis in section profile g) is µm and nm, respectively. d–g) Reproduced with permission . Copyright 2016, American Chemical Society.…”

“…In this high‐velocity region, large‐area monolayers to hexalayer microstripes with a perfect lateral continuity and thickness uniformity can be obtained. To further establish a core rule for the controllable growth of 2DMCs with good material generality via dip‐coating, Wu et al developed a model for balanced competitive processes to show how three dynamic factors influence the growth of ultrathin films (Figure d–g) . In a dip‐coating process using a low‐concentration solution, an essential prerequisite for deposition is the balance between nucleation rate and recession rate, and the balance between the nucleation rate and the assembly rate enables the growth of highly uniform ultrathin films via intermolecular self‐organization.…”

Highly crystalline and uniform conjugated polymer thin films by a water-based biphasic dip-coating technique minimizing the use of halogenated solvents for transistor applications

“…14,15 This method is advantageous for the preparation of uniform and smooth thin lms on various curved exible substrates as well as for providing ne control over conjugated polymer crystallization processes that empower efficient charge carrier transport. [16][17][18][19][20] The dip-coating process is not readily scaled-up, however, because a large volume of the polymer solution is required to ll the dip-coating reservoir. To overcome this problem, a novel biphasic dip-coating method was developed using a phase-separated solvent system composed of a reusable inert liquid support phase (the majority of the system) and the solution to be deposited, oating on top of the support phase.…”