应兰州大学材料与能源学院邀请，德国埃尔兰根-纽伦堡大学终身研究员吴明健博士将为我院做学术报告，欢迎广大师生参加。

报告题目：Unravel the structure of molecular crystals in organic semiconductors using analytical TEM, 3D electron diffraction and 4D-STEM

主讲人：吴明健

邀请人：穆晓柯 教授

时间：2025年8月20日(周三) 9:30-11:00

地点：逸夫生物楼114

报告摘要：Harnessing the complex nano-scale structure in organic semiconductors is essential to tailor their functionality and performance. For example, the orientation of π-stacking domains and grain boundaries are essential to their electric transport properties in organic field-effect transistors (OFET); in bulk hetero-junction (BHJ) organic solar cells (OSCs) it determines exciton dissociation and charge carrier pathways thus dictate performance of the cells. These structural properties at different length scales are highly sensitive to processing conditions and protocols. Unravel the structure of organic semiconductors from molecular to device scale is essential to establish the processing-structure-properties relationship. Fast electrons interact strongly with matter and can deliver a multitude of structural and analytical signals to study the structure, chemistry and composition of materials at high spatial resolution. Modern electron microscopes, as “a synchrotron in a microscope” [1], hold the potential for such studies. However, direct observation of structures of organic semiconductors using electron microscopy face certain challenges including radiation damage, limitations due to sample geometry and yet-to-established workflows etc.

In this talk, I will report our efforts toward systematically and correlatively characterize the structure of OSCs and organic semiconductor thin films using TEM: from nano-morphology of OSC using analytical methods (with energy-filtered TEM or spatially resolved electron energy-loss spectroscopy) [2], to evaluating their texture with EF-SAED (energy-filtered selection area electron diffraction) and 3D electron diffraction [3, 4]. The results are compared to that from identical sample using established X-ray based method using lab and synchrotron sources. [4] Finally I will showcase probing local structure information with our recently proposed, dose-efficient method 4D-scanning confocal electron diffraction (4D-SCED) technique [5]. Furthermore, I will discuss the merit when this technique is coupled to a state-of-the-art hybrid-pixel direct electron detector [6]. The unique combination of imaging, diffraction and spectroscopy methods in a single instrument of TEM enables straightforward, correlative study of organic semiconductors [4].

Refs:

[1] Ramasse, Q. Ultramicroscopy. 180 (2017) 41

[2] Rechberger, S., et. al., Solar RRL. 4 (2019) 1

[3] Hawly, T., et. al., ACS Appl. Mater Interf. 14 (2022) 16830

[4] Kraus, I., et. al., arXiv:2502.11254 (2025)

[5] Wu, M., et. al., Nat. Commun. 13 (2022) 2911

[6] Wu, M., et. al., J Phys. Mater. 6 (2023) 045008

报告人简介： 吴明健博士现任德国埃尔兰根-纽伦堡大学微纳结构研究所的终身职位研究员。他在湖南大学获得材料科学学士与硕士学位；在德国柏林洪堡大学以最高荣誉（summa cum laude）获得实验物理学博士学位。作为一位执着的“纳米摄影师”，吴博士在电子显微学领域拥有超过15年的研究经验。他的专长于开发和应用先进的显微、衍射与谱学技术，并将其与原位（in situ）、工况（operando）及数据科学方法相结合，以深入揭示功能材料的独特性质和构效关系。他目前的研究主要集中在有机半导体领域，尤其是针对辐照敏感材料的研究方法与技术开发。迄今为止，他已发表约90篇同行评议的学术论文。2023年，他因在开发有机薄膜材料的电镜表征的4D-SCED方法发展方面的突出贡献，荣获欧洲显微学会“杰出论文奖”。