Exciton Dissociation Dynamics at Organic-Organic and Organic-Inorganic Semiconductor Heterojunctions

技术支持：本计画旨在探讨有机-有机或有机-无机混合半导体界面激子解离的基本机制。这些包括能量驱动力，电子耦合强度，和核重组能在界面电子转移，成对形成的潜在作用，和电荷重组竞争的动态通道。飞秒时间分辨双光子光电子能谱（TR-2 PPE）将用于探测有序有机-有机或有机-无机界面处的激子解离动力学。单晶衬底和高度有序的晶体薄膜的使用最大限度地减少了纳米结构材料的异质性问题;模型系统的例子包括在单晶C60和ZnO表面上的低聚噻吩和并五苯。TR-2 PPE实验将允许人们在时间、能量和动量空间中直接跟踪电子，因为它在供体材料中以激子的形式被激发，因为它在去往受体的途中，因为它在供体/受体界面上形成成对，并且因为它在受体中弛豫。长期目标是建立太阳能电池有机异质结激子解离和电荷分离的基本原理和设计规则。非技术性：该项目涉及具有高技术相关性的材料科学主题领域的基础研究问题，预计将填补有机太阳能电池开发方面的重要知识空白。开发具有经济竞争力的太阳能技术是本世纪最重要的科学和技术挑战之一。从教育的角度来看，该项目将为参与的学生提供一个鼓舞人心的机会，从事具有科学挑战性和社会责任感的研究。PI已经建立了一个跟踪记录，并将继续不仅在教育研究生，而且在激励和参与本科生和高中生的研究。PI还将开发一个新生研讨会课程，重点是太阳能和环境挑战。

Technical: This project aims to investigate fundamental mechanisms governing exciton dissociation at organic-organic or organic-inorganic hybrid semiconductor interfaces. These include energetic driving force, electronic coupling strength, and nuclear reorganization energy in interfacial electron transfer, the potential roles of geminate pair formation, and charge-recombination as competing dynamic channels. Femtosecond time-resolved two-photon photoemission spectroscopy (TR-2PPE) will be used to probe exciton dissociation dynamics at well-ordered organic-organic or organic-inorganic interfaces. The use of single crystal substrates and highly ordered crystalline thin films minimizes heterogeneity problems in nanostructured materials; examples of model systems include oligothiophene and pentacene on single crystal C60 and ZnO surfaces. A TR-2PPE experiment will allow one to directly follow the electron in time, energy, and momentum spaces as it is excited in the form of an exciton in the donor material, as it is en route to the acceptor, as it forms a geminate pair across the donor/acceptor interface, and as it relaxes in the acceptor. The long-term objective is to establish fundamental principles and design rules for exciton dissociation and charge separation at organic heterojunctions for solar cells.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to fill an important knowledge gap in the development of organic solar cells. Developing solar energy technologies that are economically competitive is one of the most important scientific and technological challenges in this century. From an educational perspective, the project will provide an inspiring opportunity for participating students to work on scientifically challenging and socially responsible research. The PI has established a track record and will continue not only in educating graduate students, but also in motivating and involving undergraduates and high school students in research. The PI will also develop a freshman seminar course which focuses on solar energy and the environment challenges.