Photophysical Studies of Conjugated Chromophores on Peptide Templates

技术：该项目旨在解决与共轭聚合物和低聚物的固态光物理学相关的基本问题，这些问题在光电器件应用中具有广泛的兴趣。问题是：为什么共轭聚合物薄膜中的光致发光（PL）量子产率远低于溶液中，即使薄膜中的激发寿命至少一样长？在相邻共轭段上具有不相关自旋的成对电荷的多少会重新组合形成单重态激发态？这是如何依赖于形态的？在有机光伏的典型供体/受体系统中，光激发后的能量转移和间色团态的形成是否与电荷转移相竞争？在该项目中，特拉华大学的Kristi Kiick团队将合成刚性肽作为支架，通过与适当放置的非天然氨基酸反应，将共轭低聚物放置在肽的特定位置。罗彻斯特大学的刘易斯·罗斯伯格小组将使用稳态和瞬态光谱来测量改变发色团的相对位置和方向是如何改变光物理的。通过改变肽支架上两个相同的低聚物之间的距离，可以模拟共轭聚合物从稀释溶液到薄膜的光物理行为。该项目旨在测量荧光有机发光二极管技术中的限制因素——电荷重组中的单线态-三重态分支，以确定能量转移是否以及何时可以与电荷转移竞争，以及光诱导电荷分离效率的后果，并找出在有机光伏的供体/受体系统中，间色团物种的光产生是否可以抑制电荷产生。非技术：该项目涉及具有高技术相关性的材料科学专题领域的基础研究问题，并有望提供关于如何为电致发光器件应用最佳组织发色团的说明性信息。该项目为学生提供了一个高度协作和跨学科的环境训练，包括有机合成，材料表征和激光光谱学。让学生参与密切协调的合作研究是他们训练的重要组成部分，在材料科学方面尤其有价值。

Technical: This project aims to address basic questions that arise in connection with the solid-state photophysics of conjugated polymers and oligomers, which are of broad interest in optoelectronic device applications. The questions are: Why is the photoluminescence (PL) quantum yield in conjugated polymer films so much lower than in solution even though the excited lifetimes are at least as long in the films? What fraction of paired charges with uncorrelated spins on adjacent conjugation segments will recombine to form singlet excited states and how does this depend on morphology? Do energy transfer and formation of interchromophore states following photoexcitation compete with charge transfer in donor/acceptor systems typical of organic photovoltaics? During the project, Kristi Kiick's group at the University of Delaware will synthesize rigid peptides as scaffolds where conjugated oligomers can be placed at specific places on the peptide through reactions with judiciously placed non-natural amino acids. Lewis Rothberg's group at the University of Rochester will perform steady-state and transient spectroscopy to measure how the altering the relative positions and orientations of the chromophores changes the photophysics. By changing the distance between two identical oligomers on a peptide scaffold, it is possible to simulate the photophysical behavior of conjugated polymers as they go from dilute solution to films. The project is designed to measure singlet-triplet branching in charge recombination that is a limiting factor in fluorescent organic light-emitting diode technology, to determine whether and when energy transfer can compete with charge transfer and what the consequences are for efficiency of photoinduced charge separation, and to find out whether photogeneration of interchromophore species can suppress charge generation in donor/acceptor systems characteristic of organic photovoltaics.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to provide prescriptive information on how chromophores would be best organized for electroluminescent device applications. This project provides student training in a highly collaborative and interdisciplinary environment, including organic synthesis, materials characterization, and laser spectroscopy. Involving students in closely coordinated collaborative research is an important part of their training and especially valuable in materials science.