CAREER: CAS: Broadband UV-NIR Ultrafast Photochemistry Imaged in Space and Time

在化学系化学结构、动力学和机制(CSDM-A)计划的支持下，维克森林大学的Elham Ghadiri正在推进时间分辨显微镜，并使用它们来可视化太阳能集光材料中发生的基本光化学电荷转移过程是如何受到当地环境微观结构的影响的。然而，捕捉这些电荷转移过程是具有挑战性的，因为它们发生的时间接近十亿分之一秒，而且在纳米尺度的材料中，时间尺度从一个点到另一个点不同。加迪里博士和她的学生正在开发飞秒光学显微镜技术，这种技术可以直观地显示由富含地球的材料制成的集光半导体中的基本光化学反应。他们的发现可能有助于更好地了解发生在高度不均匀材料中的复杂光化学过程，并有助于制定用于未来清洁能源发电和储存应用的高效光收集材料的设计标准。与WFU可持续发展项目合作，Ghadiri小组将利用基于研究的教育平台参与社区推广，旨在教育所有年龄段的人可持续太阳能设备在日常生活中的作用，作为缓解气候变化的一个方面。Ghadiri团队将开发超快显微镜和光谱方法，以可视化复杂和非均相太阳能转换材料中的基本光致反应动力学。主要的关注点是高吸光性和基于地球丰富元素的半导体，这使它们成为可持续能源转换应用的有前途的候选者。用这种材料制造的太阳能电池的性能取决于超快和快速电子和质子转移反应的效率，这些反应相互独立地发生，也相互竞争。超快瞬时吸收和漫反射显微镜将用于探测具有宽光谱覆盖的亚微米长度尺度和超快时间尺度上的动力学。该项目旨在对对太阳能电池功能至关重要的载流子过程进行深入的时空分析。突破传统时间分辨光谱学极限的显微镜工具的进步是这项工作潜在的更广泛的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Elham Ghadiri of Wake Forest University is advancing time-resolved microscopies and using them to visualize how the fundamental photochemical charge-transfer processes taking place in solar light-harvesting materials are affected by the microscopic structure of their local surroundings. Capturing these charge-transfer processes is challenging, however, as they take place in times approaching a millionth of a billionth of a second, and the time scales vary from one point to another in a material on nanometer length scales. Dr. Ghadiri and her students are developing femtosecond optical microscopy techniques that can visualize the fundamental photochemical reactions in light-harvesting semiconductors made from earth-abundant materials. Their discoveries could lead to a better understanding of complex photochemical processes that take place in highly heterogenous materials, as well as help to develop design criteria for efficient light-harvesting materials used in future clean energy generation and storage applications. In partnership with the WFU sustainability program, the Ghadiri group will engage in community outreach using research-based educational platforms designed to educate people of all ages about the role of sustainable solar devices in daily life as one aspect of climate change mitigation. The Ghadiri group will develop ultrafast microscopy and spectroscopy methods to allow the visualization of fundamental photoinduced reaction dynamics in complex and heterogeneous solar energy conversion materials. The primary focus is on semiconductors that are highly light-absorbing and that are based on earth-abundant elements, which makes them promising candidates for sustainable energy conversion applications. The performance of solar cells fabricated from the materials depends on the efficiency of ultrafast and fast electron and proton transfer reactions that occur independently, and in competition with each other. Ultrafast transient absorption and diffuse reflectance microscopies will be used to probe the dynamics on sub-micron length scales and ultrafast time scales with broad spectral coverage. The project aims to provide an in-depth spatiotemporal analysis of charge carrier processes that are central to solar cell function. The advancement of microscopy tools that push the limits of conventional time-resolved spectroscopy is a potential broader impact of the work.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.