Monolayer organic crystals have the characteristics of low density of defect states and no grain boundaries, which make them have important application prospects in the field of optoelectronic devices. Meanwhile, single crystals with large size and high crystalline quality facilitate the controllable fabrication of organic devices, reveal the relationship between molecular arrangement and electrical properties, and ultimately provide theoretical guidance for the construction of high-performance organic optoelectronic devices. Therefore, the study of controllable preparation of monolayer organic crystals with large size and high crystalline quality as well as their electrical properties has great practical significance. At present, the water/air interface can be used as a template for the epitaxial growth of two-dimensional organic crystals, realizing the preparation of single-layer organic crystals by liquid-phase method. However, the reported methods (Langmuir-Blodgett method and liquid phase epitaxy method) still have some problems, such as poor organic solvent diffusion ability and weak intermolecular interaction force, so that the crystalline quality or size of monolayer organic crystals still remains non-ideal, and difficult to apply to large-scale optoelectronic devices.

Based on the above scientific problems, the team of Prof. Jiansheng Jie of Soochow University has made active and beneficial explorations on the growth of high-quality, large-scale monolayer organic crystals and their application in high-performance field effect devices,and used graphene quantum dots to induce organic molecules for the first time. The self-assembly method enables the controllable preparation of single-layer organic crystals with centimeter-scale dimensions and high crystalline quality. This work has the following innovations: 1. The pH value of the aqueous solution of graphene quantum dots is effectively regulated, and the controllable diffusion of organic solvents on the water surface is realized; 2. The π-π interaction force between graphene quantum dots and organic molecules can be reduced 3. Taking C10-BTBT molecule as an example, the mobility of high crystalline quality, centimeter-scale C10-BTBT monolayer crystal is as high as 2.6 cm2 V-1 s-1, which is higher than the current one. The mobility of monolayer organic crystals obtained by the reported method has a certain improvement (Langmuir-Blodgett method <0.01 cm2 V-1 s-1, liquid phase epitaxy <0.022 cm2 V-1 s-1 and rigid substrate self-assembly method 0.1-1 cm2 V-1 s-1). The researchers believe that this study will provide new ideas for the controllable growth of high-quality, large-scale monolayer organic crystals and the exploration and application of large-scale, high-performance organic field effect devices. The related paper was published in Adv. Mater. (DOI: 10.1002/adma.202003315), of which the corresponding author is Prof. Jiansheng Jie and the first author is Dr. Jinwen Wang.