A General Method for Growing Two‐Dimensional Crystals of Organic Semiconductors by “Solution Epitaxy”

Abstract

Two-dimensional (2D) crystals of organic semiconductors (2DCOS) have attracted attention for large-area and low-cost flexible optoelectronics. However, growing large 2DCOS in controllable ways and transferring them onto technologically important substrates, remain key challenges. Herein we report a facile, general, and effective method to grow 2DCOS up to centimeter size which can be transferred to any substrate efficiently. The method named "solution epitaxy" involves two steps. The first is to self-assemble micrometer-sized 2DCOS on water surface. The second is epitaxial growth of them into millimeter or centimeter sized 2DCOS with thickness of several molecular layers. The general applicability of this method for the growth of 2DCOS is demonstrated by nine organic semiconductors with different molecular structures. Organic field-effect transistors (OFETs) based on the 2DCOS demonstrated high performance, confirming the high quality of the 2DCOS.

High‐Performance Proximity Sensors with Nanogroove‐Template‐Enhanced Extended‐Gate Field‐Effect Transistor Configuration

“…To realize this goal, many strategies have been reported, including improving the crystallinity in semiconducting layer by anti-solvent crystallization, [12] solution epitaxy, [16] off-center spin coating, [8] floating film transfer, [17] solvent vapor annealing [18] and solvent exchange, [19] aligning semiconducting molecules along one specific direction by solution shearing [11] and pre-oriented templates, [20] and optimizing semiconductor/insulator interface by self-assembled monolayer [21] and phase separation between semiconductor/ insulator blends. To realize this goal, many strategies have been reported, including improving the crystallinity in semiconducting layer by anti-solvent crystallization, [12] solution epitaxy, [16] off-center spin coating, [8] floating film transfer, [17] solvent vapor annealing [18] and solvent exchange, [19] aligning semiconducting molecules along one specific direction by solution shearing [11] and pre-oriented templates, [20] and optimizing semiconductor/insulator interface by self-assembled monolayer [21] and phase separation between semiconductor/ insulator blends.…”

Surficial Marangoni Flow‐Induced Growth of Ultrathin 2D Molecular Crystals on Target Substrates

“…[9,13] Compared to the growth of 1D organic crystals (e.g., wires, ribbons), growth of ultrathin 2DMCs requires suppression of "coffee-ring" effect during the process of solvent evaporation to ensure uniform molecule spreading. [24] In this method, when the organic solution with low surface tension was dropped on the water (a high surface tension media), the solution would spontaneously and rapidly spread on the water surface by the local surface tension gradients, which is well known as a Marangoni effect. [24] In this method, when the organic solution with low surface tension was dropped on the water (a high surface tension media), the solution would spontaneously and rapidly spread on the water surface by the local surface tension gradients, which is well known as a Marangoni effect.…”

“…[24] In this method, when the organic solution with low surface tension was dropped on the water (a high surface tension media), the solution would spontaneously and rapidly spread on the water surface by the local surface tension gradients, which is well known as a Marangoni effect. [24][25][26][27] Herein, we report a surficial Marangoni flow-induced selfassembly (SMFIS) method for the fabrication of 2DMCs directly on target substrates. Li and coworkers further enhanced the spreading of the organic solution on the water by decreasing the interfacial surface tension between the water and organic solution, [25,26] and fewlayered or even monolayer 2DMCs were successfully obtained on the water surface.…”

Enhanced performance of field-effect transistors based on C60 single crystals with conjugated polyelectrolyte

“…However, for the crystallization of the C60 ribbon crystals, the crystal width decreases together with the thickness, resulting in smaller contact areas between the ribbons and electrodes and, thus, higher Rc [50]. As such, crystallization methods for extended thin single crystals are in need of exploration [59,60]. With reduced access resistance as well as the contact resistance, the mobility should further increase.…”