Optical Excitations in Aggregates, Films and Crystals of Conjugated Oligomers and Polymers

该基金由材料研究部门的材料理论项目和化学部门的理论与计算化学项目共同资助。理论研究的重点是π共轭聚合物及其相关低聚物的薄膜。这些材料作为基于有机的场效应晶体管和有机发光二极管（OLED）的有源元件受到广泛关注。尽管许多实验旨在揭示低聚物/聚合物薄膜产生光的机制，但对光发射（和吸收）的基本理解还远远没有完成。在这项资助中，实施了一项策略，从理论上研究低聚物和聚合物纳米聚集体、薄膜和晶体的光吸收和发射。重点将主要放在低聚苯基乙烯（OPVn）和低聚噻吩（Otn）及其母体聚合物上。分析将基于从已知晶体结构中获得的带有分子填料的人字形聚集体。哈密顿量包括分子间（激子）相互作用，具有多个分子内模式的线性激发-振动耦合，以及点缺陷和结构缺陷的影响。将采用双粒子近似将基集减少到可处理的大小，以进行数值分析，而不牺牲精度。该基金由材料研究部门的材料理论项目和化学部门的理论与计算化学项目共同资助。这项对有机材料的电子和光学性质的基础研究可能会导致对聚合物（塑料）光电子学及其作为器件的可能应用的新理解。＊＊＊

This grant is funded jointly by the Materials Theory Program in the Division of Materials Research and the Theoretical and Computational Chemistry Porgram in the Chemistry Division. The theoretical research focuses on thin films of pi-conjugated polymers and their associated oligomers. These materials are receiving widespread attention as the active components for organic-based field effect transistors and organic light emitting diodes (OLED's). Despite the many experiments designed to reveal the mechanism(s) by which oligomer/polymer films produce light, a fundamental understanding of light emission (and absorption) is far from complete. In this grant a strategy is implemented to theoretically investigate light absorption and emission in oligomer and polymernanoaggregates, films and crystals. The focus will be primarily on oligo-phenylenevinylene (OPVn) and oligo-thiophene (Otn) and their parent polymers. The anaylsis will be based on herringbone aggregates with molecular packing derived from known crystal structures. The Hamiltonian includes intermolecular (excitonic) interactions, linear excition-vibrational coupling with multiple intramolecular modes, and the influence of point and structural defects. The two-particle approximation will be employed to reduce the basis set to a tractable size for numerical analysis without sacrificing accuracy. %%% This grant is funded jointly by the Materials Theory Program in the Division of Materials Research and the Theoretical and Computational Chemistry Program in the Chemistry Division. This fundamental research on the electronic and optical properties of organic materials may lead to a new understanding of polymeric (plastic) optoelectronics and their possible applications as devices. ***