Understanding the Roles of Intra- and Interchain Order on Spin-Dependent Electronic Processes in Self-Assembled Conjugated Polymer Aggregates

了解链内和链间有序对自组装共轭聚合物聚集体中自旋相关电子过程的作用

• 批准号: 1506558
• 负责人: John Grey
• 金额: $ 43.5万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506558&HistoricalAwards=false
• 关键词: Understanding; Roles; Intra; Interchain; Order

With this award, the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division is supporting Professor John Grey of the University of New Mexico to study spin-dependent processes in self-assembled polymeric systems. Conjugated polymers are large chains consisting of a basic molecular repeat unit that absorb light and conduct charges making them excellent candidates for next-generation optoelectronic applications. For example, these so-called 'plastic' semi-conductors are used in solar cells and light emitting displays, which may eventually replace existing technologies owing to their ever increasing efficiencies over the last 10 years and relatively low cost. The ways in which the polymer chains fold and pack in thin films has a significant impact on the overall performance of organic solar cells and light-emitting devices (OLEDs). The proposed research will use new strategies to fabricate ordered polymer structures and study how electrical charges are formed and how electrical current can be generated more efficiently in the resulting films. In addition, the PI and his NSF-sponsored graduate students actively participate in ongoing educational and research infrastructure development programs at the University of New Mexico. These activities include coordinating with the local Center for Integrated Nanotechnologies (CINT) to increase the participation of undergraduate and graduate researchers through collaboration with CINT staff scientists. Students take part by writing user proposals that undergo peer review thus providing valuable experience in designing and executing an independent research project. Lastly, student participants gain valuable and diverse skill sets in academic fields essential for national interests. The interactions between and inter-conversion of electrically neutral (exciton) and charged (polaron) states of different spin in conjugated polymer materials has significant bearing on their overall performance in cutting-edge optoelectronic devices, such as solar cells. Although the outcomes of these processes are strongly dependent on polymer structure, detailed molecular level structure-function relationships have proven difficult to obtain from conventional polymer functional forms (i.e., bulk thin films). This difficulty originates from morphological heterogeneity due to intrinsic molecular weight poly-dispersity of polymers. The proposed research seeks to overcome heterogeneity effects to understand how molecular structure regulates interactions and inter-conversion of excitonic and polaronic spin states. Self-assembly approaches are used to fabricate well-defined polymer aggregate supramolecular nanostructures that can be exploited to selectively control conformational and packing (intra- and interchain) order and electronic coupling. The Grey group at the University of New Mexico has pioneered this approach to direct exciton coupling and polaron interactions in polymer aggregates that are leveraged in the proposed research to address longstanding fundamental questions involving spin state exchange interactions and crossover in polymeric semiconductors. This research also takes new directions for interrogating the fates and interactions of different spin states in individual polymer nanostructures by introducing sensitive and selective electric- and magnetic-field dependent molecular spectroscopic and imaging techniques. The research aims to establish design rules for reliably tuning subtle polymer chain packing and order within supramolecular assemblies to understand and control exchange interactions and spin state inter-conversion for improved material performance.

化学部的大分子、超分子和纳米化学项目将利用该奖项支持新墨西哥大学的约翰·格雷教授研究自组装聚合物体系中的自旋依赖过程。共轭聚合物是由基本分子重复单元组成的大链，可以吸收光并传导电荷，使其成为下一代光电应用的绝佳候选者。例如，这些所谓的“塑料”半导体用于太阳能电池和发光显示器，由于它们在过去10年里效率不断提高，成本相对较低，最终可能取代现有的技术。聚合物链在薄膜中的折叠和封装方式对有机太阳能电池和发光器件（oled）的整体性能有重要影响。提出的研究将使用新的策略来制造有序的聚合物结构，并研究电荷是如何形成的，以及如何在所产生的薄膜中更有效地产生电流。此外，PI和他的nsf资助的研究生积极参与新墨西哥大学正在进行的教育和研究基础设施发展项目。这些活动包括与当地的集成纳米技术中心（CINT）协调，通过与CINT工作人员的合作，增加本科生和研究生研究人员的参与。学生通过撰写经过同行评审的用户建议来参与，从而为设计和执行独立研究项目提供宝贵的经验。最后，学生参与者获得了对国家利益至关重要的学术领域的宝贵和多样化的技能。共轭聚合物材料中不同自旋的电中性态（激子）和带电态（极化子）之间的相互作用和相互转换对其在尖端光电器件（如太阳能电池）中的整体性能具有重要影响。尽管这些过程的结果强烈依赖于聚合物结构，但事实证明，从传统的聚合物功能形式（即大块薄膜）中很难获得详细的分子水平结构-功能关系。这种困难源于聚合物固有分子量的多分散性所导致的形态异质性。提出的研究旨在克服异质性效应，以了解分子结构如何调节激子和极化子自旋态的相互作用和相互转换。自组装方法用于制造定义良好的聚合物聚集体超分子纳米结构，可用于选择性地控制构象和包装（链内和链间）顺序和电子耦合。新墨西哥大学的Grey小组率先采用了这种方法，在聚合物聚集体中直接激子耦合和极化子相互作用，在提出的研究中利用这种方法来解决涉及聚合物半导体中自旋态交换相互作用和交叉的长期基本问题。本研究还通过引入敏感和选择性的依赖于电场和磁场的分子光谱和成像技术，为探究单个聚合物纳米结构中不同自旋态的命运和相互作用开辟了新的方向。该研究旨在建立设计规则，以可靠地调整超分子组装中的细微聚合物链排列和顺序，以了解和控制交换相互作用和自旋态相互转换，从而提高材料性能。