学术讲座
报告题目：Charge Carrier (De)localization in Two-Dimensional Organic Crystals
报告时间：2023-10-11 10:00
报告人： 王海 助理教授
Utrecht University
报告地点：翔安校区能源材料大楼3号楼大报告厅
转播地点：思明校区同安二106教室
报告摘要：
Conventional semiconducting polymers exhibit localized, hopping-like charge transport with reported state-of-the-art electrical mobility on the order of 1 cm2 V-1 s-1, partially owing to the disordered nature of polymer blends.1 Developing long-range order organic structures, e.g., organic small molecule crystals or covalent/metal organic frameworks (COFs/MOFs) with extended electronic states facilitates delocalized transport towards highly mobile organic electronics. The charge transport mechanisms in these emerging classes of organic crystals on the other hand remain elusive. I would like to present our recent advances in understanding transient or full delocalization of charge carriers in novel 2D organic crystals2-4 with varied intermolecular bonding or coupling strength. First, for organic crystals bonded by strong intermolecular forces (e.g., covalently in COFs or MOFs), employing temperature-dependent, time- and frequency-resolved terahertz spectroscopy, we show that charge carriers can be fully delocalized and undergo coherent band transport2-3, in analogy to fully delocalized charge-carrier behaviors in highly conductive inorganic layered 2D materials4. The short-range carrier mobility in OFs can go up to 1000s cm2 V-1s-1, vastly outperforming state-of-the-art conductive organic semiconductors. Second, for 2D organic crystals linked by weak intermolecular forces (e.g., van der Waals forces in small molecular crystals), the reported charge carrier mobility can reach up to ~10 cm2 V-1s-1, lying in an intermediate mobility regime that neither band-like nor hopping-like transport describe the charge transport effects. Combing THz spectroscopy and quantum-chemistry simulation, we show that transient localization/delocalization scenario: a theory that has been recently proposed5, can perfectly capture the temperature-dependent charge transport in two exemplary small molecule crystals (DNTT and c8-DNTT-C8)6. Our results thus extend our current understanding of charge transport effects in semiconducting polymers (e.g., by hopping), into transient or fully delocalization effects in a range of organic crystals, relevant for developing high-mobility organic electronics.
References
(1). Schweicher, G. et al. Adv. Mater., 2020, 32, 1905909; (2). S. Fu, H. I. Wang* et al. J. Am. Chem. Soc., 2022, 144, 7489-7496; (3). M. Wang, H. I. Wang*, X. Feng* et al. Nat. Matt., 2023, 22, 880–887; (4). W. Zheng, W.; H. I. Wang*, M. Bonn* et al. Nat. Phys., 2022, 18, 544; (5). S. Fratini et al. Adv. Funct. Mater. 2016, 26, 2292-2315; (6). M. Giannini, H. I. Wang*, D. Beljonne* et al. Nat. Matt., 2023, in press; https://doi.org/10.1038/s41563-023-01664-4.
报告人简介：
Dr. Hai Wang studied Materials Science at Zhejiang University in 2003-2009. Between 2009 and 2011, he finished a joint master's program in Nanoscience at KU Leuven and TU Delft, supported by the Erasmus Mundus fellowship. In 2012-2016, Hai conducted his PhD research with Prof. Mischa Bonn at Max Planck Institute for Polymer Research (MPI-P). After a postdoc with Prof. Dr. Kläui at Mainz University, Hai started an independent research group “Nano- optoelectronic materials” at MPI-P in 2017. Since June of 2023, Hai has moved to Utrecht University in the Netherlands as an assistant professor. Employing ultrafast THz spectroscopy, Hai’s research theme lies in understanding fundamental charge carrier dynamics in low-dimensional materials and interfaces, relevant for energy and (opto)electronic applications.
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