Spectroscopic characterization of the exciton coherence lengths and dynamics in organic molecular crystalline materials

加州大学河滨分校的Christopher Bardeen在实验物理化学项目的支持下开展了一项研究，旨在了解是否有可能利用量子离域（单线态激子）或长寿命（三重态激子和准分子）来显着改善有机材料的能量传输特性。该研究计划旨在实现三个目标。首先，分子晶体材料中单线态激子的电子结构和动力学作为单体结构和形态的函数将被确定，利用温度依赖的时间和波长分辨荧光。其次，其他类型的长寿命激发态的动力学，特别是三重态和准分子，将在分子晶体材料中进行研究。第三，将开发一种双光子驻波方法来直接测量标准太阳能电池几何形状晶体材料中的有效激子扩散长度。在前两个目标中获得的光物理理解有望成为解释光电流产生如何依赖于有机薄膜内激发位置的基础。本研究项目旨在提高我们对共轭有机材料中能量输运过程的理解。这种理解反过来又有助于改进太阳能电池材料的设计，从而解决一个重要的社会问题：对清洁、廉价和可再生能源的需求。研究生和博士后将在技术关键领域进行培训。此外，还将与河滨当地一所中学的学生一起开发和实施一项实际操作的光/太阳能示范。

Christopher Bardeen of the University of California-Riverside is supported by the Experimental Physical Chemistry Program to carry out research that aims to understand whether it is possible to take advantage of quantum delocalization (singlet excitons) or long lifetimes (triplet excitons and excimers) to significantly improve the energy transport properties of organic materials. The research plan is designed to accomplish three objectives. First, the electronic structure and dynamics of singlet excitons in molecular crystal materials as a function of monomer structure and morphology will be determined, utilizing temperature-dependent time- and wavelength-resolved fluorescence. Second, the dynamics of other types of longer-lived excited states, specifically triplets and excimers, will be investigated in molecular crystal materials. Third, a two-photon standing wave approach will be developed to measure directly the effective exciton diffusion length in crystalline materials in standard solar cell geometries. The photophysical understanding obtained in the first two objectives is expected to form the basis of the interpretation of how photocurrent generation depends on excitation position within organic thin films. This research project is designed to improve our understanding of energy transport processes in conjugated organic materials. This understanding in turn could aid in the design of improved materials for solar cells, and thus address an important societal problem: the need for clean, inexpensive, and renewable energy. Graduate students and postdoctoral associates will be trained in technologically vital areas. As well, a hands-on light/solar energy demonstration will be developed and implemented with students at a local middle school in Riverside.