Two-dimensional (2D) organic semiconductor crystals are an important type of organic ultra-thin crystals. Owing to their advantages of low defects, long-range molecular arrangement, high charge transfer efficiency, and solution processing capabilities, they are an important tool for revealing the intrinsic properties of materials and building optoelectronic or photonic devices. However, single-component 2D organic crystals can only achieve a single function and cannot meet the current development needs of highly integrated optoelectronics applications. Therefore, two or more organic single crystals are created into 2D organic lateral heterostructures through epitaxial growth methods, thereby achieving spatial modulation of chemical components and their optoelectronic properties, which is important for the development of 2D organic crystals and the construction of optoelectronic and photonic devices. In principle, the preparation of 2D organic lateral heterostructures can be achieved by epitaxially growing another organic crystal at the edge of the existing crystal. Although conceptually simple, the preparation of 2D organic crystal lateral heterostructures remains a considerable challenge due to the difficulty in controlling the nucleation sites and orientations of the two crystals.
Based on the above challenges, recently, Prof. Liang-Sheng Liao and Prof. Xue-Dong Wang from the Institute of Functional Nano and Soft Materials of Soochow University and Prof. Min Zheng from the College of Textile and Clothing Engineering of Soochow University have proposed a two-step strategy that combines liquid-phase growth approach and vapor-phase growth method, 2D organic lateral heterostructures were designed and synthesized. Through the above design strategy, on the one hand, perylene (Pe) crystals and 3-perylenecarboxaldehyde (PeO) crystals can nucleate and grow epitaxially under the synergistic effect of binary solvents, thus forming a Pe–PeO lateral heterostructure; on the other hand, due to the Pe–PeO heterostructure has good chemical component distribution in a very small area, it as a precursor for the vapor phase method, which effectively avoids disordered physical vapor deposition to form a PeO–Pe lateral heterostructure. This strategy not only combines the advantages of two methods, namely the low-cost solution process engineering and the high-quality single crystal preparation of the vapor-phase method but also realizes the structural inversion of the two-dimensional heterostructure based on the respective characteristics of the methods. The preparation of 2D organic heterostructures demonstrates the diversity and cross-fertilization of methods. In addition, growth mechanism studies show that the two-dimensional heterostructure crystal follows a spiral dislocation growth behavior, which effectively avoids the volume expansion and contraction of the organic lateral heterostructure, thereby minimizing connection defects at the heterointerface. As a conceptual application demonstration, the organic lateral heterostructure shows good light transmission capabilities and tunable spatial exciton conversion, indicating its application potential in the field of photonics. The successful preparation of several 2D organic lateral heterostructures based on polycyclic aromatic hydrocarbon molecules using a solution-phase growth method further verified the versatility of this synthetic strategy. The above results show that this strategy provides a feasible idea for the synthesis of 2D organic lateral heterostructures, and provides important material basis and method reference for creating next-generation optoelectronic devices. Relevant results have been published in the Journal of Nature Chemistry (DOI: 10.1038/s41557-023-01364-1).
Figure 1. Schematic diagram of the strategy and fluorescence microscopy images of two-dimensional organic lateral heterostructures.
Figure 2. Characterization analysis of 2D organic lateral heterostructures
Link to paper：https://www.nature.com/articles/s41557-023-01364-1
Title: Lateral epitaxial growth of two-dimensional organic heterostructures
Authors：Qiang Lv, Xue-Dong Wang*, Yue Yu, Chao-Fei Xu, Yan-Jun Yu, Xing-Yu Xia, Min Zheng* & Liang-Sheng Liao*
Link to Prof. Liang-Sheng Liao's group: http://www.funsom.com/
Editor: Guo Jia