Optical Excitations in Supramolecular Assemblies of Conjugated Oligomers and Polymers

共轭低聚物和聚合物超分子组装体中的光激发

• 批准号: 0606028
• 负责人: Francis Spano
• 金额: $ 24万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0606028&HistoricalAwards=false
• 关键词: Optical; Excitations; Supramolecular; Assemblies; Conjugated

Thin films of pi-conjugated polymers and their oligomer progeny continue to receivewidespread attention as the active materials for organic-based field effect transistors, lightemitting diodes (OLEDs) and solar cells. Despite the many experiments designed to reveal the mechanism(s) by which oligomer/polymer films interact with light, a fundamental appreciation of the relationship between solid-state morphology and photophysical behavior is lacking. In this renewal proposal a strategy is outlined for theoretically investigating an emerging class of supramolecular assemblies based on oligo-p-phenylenevinylene (OPVn) and oligo-thiophene (OTn) derivitives. Side- and end-group functionalization induces chirality and hydrogen bonding in self-assembled nanostructures including helical rod aggregates, rosette shaped aggregates and two-dimensional lamellae. Many of these structures employ p-stacking motifs whichcomplement the more common herringbone packing found in crystals and thin films of the unsubstituted OPVn and OTn molecules. Specific goals include: A detailed understanding of the impact of exciton delocalization, exciton-phonon coupling and disorder on the photo-excited and photo-emissive states in chiral aggregates. Abundant spectral data for helical rod aggregates including steady-state absorption, photoluminescence, circular dichroism (CD) and circularly polarized luminescence (CPL), allows rigorous testing of theoretical models featuring various scenarios for static disorder. A global account for the unusual demise of the CPL dissymmetry magnitude with increasing wavelength observed in OPVn-based helical rod aggregates as well as chiral polythiophene thin films is sought.A robust theoretical account of the deleterious effect of increasing oligomer length on theexciton bandwidth observed in a series of ethylene oxide end-capped OTn fibrillar aggregates (with n=5,6,7). How the bandwidth behaves into the polymer limit is crucial in understanding energy transport and optical properties in thin films of the technologically important regioregular poly(3-alkylthiophenes).Accurate modeling of rapid picosecond energy transport in helical rod aggregates as well as the temporal evolution of the emission spectral line shape following excitation abovethe optical gap. The emission spectral line shape provides valuable information about high energy emissive states. The analysis will be based on the Holstein Hamiltonian, treating excitonic interactions, linear exciton-vibrational coupling, and the influence of point and structural defects on equal footing. The two-particle approximation will be employed to reduce the basis set to a tractable size for numerical analysis without sacrificing accuracy. Excitonic polarons and their steady-state spectral signatures will be evaluated using standard numerical matrix techniques. A Pauli Master Equation will be employed for the exciton transport studies.The broader impact of the proposed activities will be felt primarily through an enhancedunderstanding of a technologically important class of materials, possibly resulting in novel design strategies for improved OLEDs and organic-based solar cells. The commercial impact of soft electronic devices is expected to dramatically increase over the next several years, through products like flexible displays, electronic labels and even solid-state lighting. In addition, the proposed activities will enhance research infrastructure through international collaborations. (D. Beljonne at the Universite de Mons, Belgium; S. Meskers at Eindoven University, The Netherlands; and C. Silva at the University of Montreal.)Non-Technical Abstract: This grant will support theoretical research on the properties of thin films of electrically active polymers. These materials have potential applications as components of electronic devices ("electronic plastics"). However, much needs to be done to understand their fundamental behavior. The work proposed here involves international collaborations with others working on these problems and provides wonderful learning opportunities for students and postdoctoral associates working on this project.

π共轭聚合物及其低聚物衍生物薄膜作为有机场效应晶体管、发光二极管（OLED）和太阳能电池的活性材料一直受到广泛关注。尽管设计了许多实验来揭示低聚物/聚合物膜与光相互作用的机制，但缺乏对固态形态和光物理行为之间关系的基本认识。在这个更新的建议，战略概述了理论上研究一类新兴的超分子组装体的基础上，低聚对苯撑乙烯（OPVn）和低聚噻吩（OTn）衍生物。侧基和端基官能化诱导自组装纳米结构中的手性和氢键，包括螺旋棒聚集体、玫瑰花状聚集体和二维层状结构。这些结构中的许多采用p-堆叠基序，其补充了在未取代的OPVn和OTn分子的晶体和薄膜中发现的更常见的人字形堆积。具体目标包括：详细了解激子离域、激子-声子耦合和无序对手性聚集体中光激发态和光发射态的影响。丰富的光谱数据的螺旋杆聚集体，包括稳态吸收，光致发光，圆二色性（CD）和圆偏振发光（CPL），允许严格测试的理论模型，具有各种场景的静态无序。在OPVn基螺旋棒状聚集体和手性聚噻吩薄膜中观察到的CPL不对称幅度随波长增加而消失的现象，在一系列环氧乙烷封端的OTn纤维状聚集体（n= 5，6，7）中观察到的低聚物长度增加对激子带宽的有害影响，得到了一个可靠的理论解释.带宽如何表现到聚合物的限制是至关重要的理解在薄膜中的技术上重要的regioregular聚（3-烷基噻吩）的能量传输和光学性质的准确建模的快速皮秒能量传输的螺旋杆聚集体以及时间演化的发射光谱线形状以下激发above的光学间隙。 发射谱线形状提供了关于高能发射态的有价值的信息。 分析将基于Holstein哈密顿量，治疗激子相互作用，线性激子振动耦合，以及点和结构缺陷的影响。 两粒子近似将被用来减少基组到一个易于处理的大小，数值分析，而不牺牲精度。激子极化子和他们的稳态光谱签名将使用标准的数值矩阵技术进行评估。激子输运研究将采用泡利主方程。拟议活动的更广泛影响将主要通过增强对一类技术上重要的材料的理解而感受到，这可能导致改进OLED和有机太阳能电池的新设计策略。软电子设备的商业影响预计将在未来几年内通过柔性显示器，电子标签甚至固态照明等产品大幅增加。此外，拟议的活动将通过国际合作加强研究基础设施。（D. Beljonne在比利时蒙斯大学;荷兰埃因多芬大学的Meskers和C.蒙特利尔大学的席尔瓦。）非技术摘要：该补助金将支持电活性聚合物薄膜特性的理论研究。 这些材料具有作为电子器件的组件（“电子塑料”）的潜在应用。 然而，需要做很多工作来了解它们的基本行为。 这里提出的工作涉及与其他人在这些问题上的国际合作，并为从事该项目的学生和博士后提供了极好的学习机会。