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

技术：该项目旨在研究控制有机-有机或有机-无机杂化半导体界面激子解离的基本机制。这些包括界面电子转移中的能量驱动力、电子耦合强度和核重组能、双键对形成的潜在作用以及作为竞争动态通道的电荷复合。飞秒时间分辨双光子光电子能谱(tr-2PPE)将用于探测有机-有机或有机-无机有序界面的激子解离动力学。使用单晶衬底和高度有序的晶体薄膜可以最大限度地减少纳米结构材料中的异质性问题；模型体系的例子包括单晶C60和氧化锌表面上的低聚并噻吩苯和并五苯。TR-2PPE实验将允许人们在时间、能量和动量空间上直接跟踪电子，因为电子在施主材料中以激子的形式被激发，当电子在到达受主的途中，当电子在施主/受主界面上形成双原子对时，当电子在受主中松弛时，电子在受主中松弛。该项目的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：该项目解决了材料科学中具有高度技术相关性的热门领域的基础研究问题，并有望填补有机太阳能电池发展中的一个重要知识空白。开发具有经济竞争力的太阳能技术是本世纪最重要的科技挑战之一。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，让他们从事具有科学挑战性和对社会负责的研究。PI已经建立了记录，并将继续不仅在教育研究生方面，而且在激励和让本科生和高中生参与研究方面。PI还将开发一门新生研讨会课程，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.