CAREER: Understanding the Role of Quantum Coherence in Exciton Transport and Separation in Molecular Aggregates

技术支持：该职业奖的研究部分探索了量子相干在有机半导体中激子传输和电荷分离中的作用。有机光伏器件通常由复杂的纳米结构制成。需要一种策略来将激子引导到供体/受体界面并将它们有效地分离。在光合复合体中，相干耦合和非相干激子捕获的相互作用为激子的传输和分离提供了一种有效的途径。对于分子晶体和π共轭聚合物，激子通过相干耦合离域是众所周知的，但几个重要问题的答案仍然不清楚。例如，激子离域将如何夸耀激子输运范围？光激发后离域尺寸在超快（1皮秒）时间尺度内是如何变化的？激子离域在电荷分离中扮演什么角色？知识差距部分是由于缺乏实验工具，可以测量激子运动所需的空间（纳米）和时间分辨率（飞秒）。为了克服这一障碍，PI使用飞秒时间分辨光电子能谱和荧光上转换光谱来测量激子输运范围、离域尺寸和界面电荷转移动力学。非技术性：该项目解决了与有机半导体相关的基本材料问题。低成本可再生能源的大规模应用是21世纪世纪的主要挑战之一。该项目通过探索可以提高下一代太阳能电池效率的机制来帮助应对这一挑战。该项目的教育活动与研究活动相结合。例如，最新的研究课题被纳入本科课程。研究机会提供给本科生以及高中学生和教师。PI和他的学生访问当地学校，通过讲座和实验演示向K-12学生介绍与可再生能源有关的基础科学。通过堪萨斯大学的成人教育方案，举办旨在提高公众对可再生能源认识的公开讲座。

Technical: The research component of this CAREER award explores the role of quantum coherence in exciton transport and charge separation in organic semiconductors. Organic photovoltaic devices are often made from complex nanostructures. A strategy is needed to direct excitons to and separate them effectively at the donor/acceptor interfaces. As recently demonstrated in photosynthetic complex, the interplay between the coherent coupling and incoherent exciton trapping could provide an effective way for exciton transport and separation. For molecular crystals and pi-conjugated polymers, it is well known that excitons delocalize through coherent coupling, but answers to several important questions remain unclear. For example, how will the exciton delocalization boast the exciton transport range? How does delocalization size change in an ultrafast ( 1 picosecond) timescale after photoexcitation? What are the roles of exciton delocalization in charge separation? The knowledge gap is partially due to the lack of experimental tools that can measure exciton motion with the required spatial (nanometer) and temporal resolution (femtosecond). To overcome this barrier, the PI uses both femtosecond time-resolved photoemission spectroscopy and fluorescence up-conversion spectroscopy to measure the exciton transport range, delocalization size, and charge transfer dynamics at interfaces.Non-technical: The project addresses fundamental materials issues related to organic semiconductors. The large-scale implementation of low cost renewable energy is one of the major challenges in the 21st century. The project helps to address the challenge through exploring the mechanisms that could improve the efficiency of next generation solar cells. The education activities in this project are integrated with the research activities. For example, up-to-date research topics are incorporated into undergraduate courses. Research opportunities are provided to undergraduates as well as high school students and teachers. The PI and his students visit local schools and introduce basic science related to renewable energy to K-12 students through lectures and experimental demonstrations. Public lectures designed to increase the public awareness of renewable energy are given through adult education programs at the University of Kansas.