Evolution of the Electronic Properties of Conjugated Materials from Isolated Molecules to Aggregates

在这个由化学系化学结构、动力学和机理计划资助的项目中，Linda Peteanu教授和她的学生将致力于更好地了解将聚合物转化为工作装置所需的化学和物理处理步骤如何影响其电荷传输和发光能力。要成功设计出最高效、轻巧、灵活的聚合物基材料，用于下一代光伏设备和低功耗照明，就需要这些知识。Peteanu小组专注于这些关键特性如何受到聚合或聚合物链之间的相互作用的影响，这些聚集或相互作用在形成固态薄膜的过程中不可避免地发生。这一建议通过光学光谱学对MEH-PPV、CN-PPV和聚荧烯电致发光聚合物的短链模型低聚物通过溶剂中毒形成的聚集体和单分子水平的聚集体进行了研究。这些低聚物聚集体是更复杂的聚合物的光谱和动力学的优秀模型系统。此外，幸运的是，它们缺乏结构缺陷，这些缺陷使解释聚合物数据变得更加困难。利用单聚集体中的光子关联和块体样品中的超快光谱测量了其发光性质和能量传递动力学。超快光谱和斯塔克光谱也被用来探测这些材料中的电荷分离和输运。然后，通过与David Yaron(CMU)合作进行电子结构计算，可以获得这些系统的结构、光谱和动力学的统一图像。这些努力不仅有助于节能设备的开发，而且有助于培训一支能够利用其商业潜力的劳动力。

In this project, funded by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Professor Linda Peteanu and her students will work towards a better understanding of how the chemical and physical processing steps required to turn a polymer into a working device affect its charge transport and light emitting capabilities. This knowledge is required for the successful design of the most efficient lightweight, flexible, polymer-based materials for next-generation photovoltaic devices and low power consumption lighting. The Peteanu group focuses on how these critical properties are impacted by aggregation or the interactions between polymer chains that inevitably occur during processing to form solid state films. This proposal addresses these issues by optical spectroscopy on the bulk and single molecule level of aggregates formed from short-chain model oligomers of the electroluminescent polymers MEH-PPV, CN-PPV and polyfluorene by solvent poisoning. These oligomer aggregates are excellent model systems for the spectroscopy and dynamics of the more complex polymers. Moreover, they fortunately lack the structural defects that make interpreting the polymer data more difficult. The light emitting properties and energy transfer dynamics are measured using photon correlation in single aggregates and ultrafast spectroscopy in bulk samples. Ultrafast spectroscopy and Stark spectroscopy are used to probe charge separation and transport in these materials as well. Electronic structure calculations in collaboration with David Yaron (CMU) then enable obtaining a unified picture of the structure, spectroscopy, and dynamics in these systems. These efforts contribute not only to the development of energy saving devices but to training of a work force that can capitalize on their commercial potential.