报告题目：Mapping Charge Carrier Dynamics: From World-Record Perovskite Solar Cells to Exceptional Performance of X-Ray Imaging Scintillators
报 告 人：Omar Mohammed，沙特阿卜杜拉国王科技大学
时 间：2024年7月19日09:00
地 点：莫干山校区化工5号楼B306
报告摘要：
The separation and collection of photo-generated charge carriers in light-harvesting devices are limited by the losses and ambiguous dynamical events at the surfaces and interfaces of the absorber layers.These events occur in ultrafast time scales and can only be visualized selectively in space and time by scanning ultrafast electron microscopy. In this method, the surface of the photoactive materials is excited by a clocking optical pulse and the photo-induced changes will be directly imaged using a pulsed electron beam that generate secondary electrons with a couple of electron volts energy, which are emitted from the very top surface of the material in a manner that is extremely sensitive to the localization of the electron and hole on the photoactive material surfaces. This powerful technique along with ultrafast laser spectroscopy allow us to directly and precisely investigate and decipher the trajectory of charge carriers on materials surfaces and interfaces in real space and real time. Through this work, we have optimized the properties of photoactive materials for applications in light-harvesting devices that led to the world-record solar cell devices based on perovskite crystals. Moreover, we have clearly demonstrated in space and time how the surface orientations, surface oxidation and passivation can significantly impact the overall dynamical processes of photo-generated charge carriers in optoelectronic materials. Finally, I will talk about our recent ground-breaking work in X-ray imaging technology that includes multicolor scintillators, cutting-edge materials discovery, heavy-atom engineering, state-of-the-art characterization and efficient interfacial energy transfer between sensitizers and scintillators that has led to the development of novel X-ray imaging screens with outstanding sensitivity, ultralow detection limit, unprecedented spatial image resolution and low-cost fabrication, with potential applications in medical imaging, industrial monitoring and security screenings.
报告人简介：
Omar Mohammed是沙特阿卜杜拉国王科技大学教授，也是超快激光光谱学和四维（4D）电子成像实验室的主要研究员。Mohammed教授主要研究方向为是利用超快激光光谱学、4D电子成像和计算材料学，开发高效太阳能电池、发光二极管和X射线成像闪烁体。Mohammed教授在SCI期刊上发表了340余篇文章，包括《Science》、《Nature》、《Nature Materials》、《Nature Energy》和《Nature Photonics》等，其论文已经获得超过39,000次引用，h-index为94。2019-2023年，Mohammed教授连续五年被Web of Science评为高被引学者。2020年1月，他加入了《Journal of Physical Chemistry Letters》的编委会。2021年2月，他被授予英国皇家S13博彩学会会士（FRSC）称号。2021年3月1日，Mohammed教授被任命为《ACS Applied Materials & Interfaces》的副编辑。2023年1月，他加入了《ACS Materials Letters》、《Journal of Physical Chemistry A & B & C》的编委会。2023年7月，他被授予物理学会（IOP）会士。此外，曾获得科威特阿拉伯经济与社会发展基金颁发的杰出学者奖、德国的长期奖学金、日本学术振兴会（JSPS）奖学金、埃及的基础科学国家奖、约旦的肖曼基金会光S13博彩奖以及科威特基金会颁发的物理学科威特奖。
