DMREF - Collaborative Research: Developing design rules for enhancing mobility in conjugated polymers

非技术性有机半导体在便携式、大面积或无处不在的电子产品中有许多应用。作为传感器或换能器中的活性材料，它们在生物电子学方面也具有巨大的潜力。所有这类器件都是通过传输电荷来工作的；因此，寻找具有大电荷迁移率的材料是有机电子领域的一个主要目标。然而，寻找高迁移率的有机半导体在很大程度上仍然是按照爱迪生的哲学进行的。拟议活动的主要目标是开发一套合理的设计原则，以创造高迁移率的共轭均聚物和共聚物，这将影响有机半导体的所有应用，从太阳能电池到发光二极管和晶体管。来自理论的见解将被用来设计和合成分子，这些分子将被用来进行实验分析，使用X射线衍射进行结构表征，并使用光学光谱来测量电荷离域。这些属性将与材料的载流能力相关。最终目标是将分子结构和组装内分子的短程排列的特定特征与载体的迁移率联系起来。开发的方法，无论是理论上的还是实验上的，都可能简化对高迁移率聚合物的搜索，并为下一代高性能有机电子设备铺平道路。功能材料的技术总结设计将基于一个理论模型，该模型考虑了电荷传输、核电子耦合以及适合于混合或分离的pi堆栈的二维晶格内对角和非对角无序的各种表现。根据理论得出的设计原理将在几种模型上进行测试，其中链内扭转无序和/或HOMO能量变化受到严格控制。将使用具有不同吸电子强度的受体来评估基于吲哚二硫吩类结构基元的高性能共聚物的结构/性能关系。用掠入射X射线衍射(GIXD)表征聚合物薄膜的微结构，用电荷调制光谱(CMS)研究取向样品的电荷离域，以获得偏振分辨率。拟议的活动将为有机电子界提供一种快速从实验和理论上评估材料的方法，用于设计高性能有机半导体。它还将首次使用稳态红外吸收光谱测量共轭聚合物中极化子的相干长度。相干长度将与新的共轭聚合物及其短程形态的设计相联系，从而为控制共轭聚合物薄膜中的离域和陷阱提供基本的见解。

NON-TECHNICAL SUMMARYOrganic semiconductors have many applications in portable, large-area or ubiquitous electronics. They also have great potential in bioelectronics as active materials in sensors or transducers. All such devices work by transporting charges; finding materials with large charge mobilities is therefore a major goal in the field of organic electronics. The search for high-mobility organic semiconductors, however, is still largely conducted with an Edisonian philosophy. The primary goal of the proposed activity is the development of a set of rational design principles for creating high-mobility conjugated homopolymers and copolymers which will impact all applications of organic semiconductors, from solar cells to light-emitting diodes and transistors. Insight derived from theory will be used to design and synthesize molecules that will be analyzed experimentally using X-ray diffraction for structural characterization and optical spectroscopy for measuring charge delocalization. These attributes will be correlated with the ability of the materials to carry current. The ultimate goal is to link specific features of the molecular structure and of the short-range arrangement of molecules within the assembly to carrier mobility. The methods developed, both theoretical and experimental, can potentially streamline the search for high mobility polymers and pave the way for the next generation of high-performance organic-based electronic devices. TECHNICAL SUMMARYRational design of functional materials will be based on a theoretical model that accounts for charge transport, nuclear-electronic coupling, and various manifestations of diagonal and off-diagonal disorder within a two-dimensional lattice appropriate for mixed or segregated pi-stacks. Design principles derived from theory will be tested on several model Donor-Acceptor copolymers in which intrachain torsional disorder and/or HOMO energy alternation is carefully controlled. Structure/property relationships will be evaluated on high-performance copolymers based on the indacenodithiophene structural motif using acceptors with varying electron-withdrawing strengths. Microstructural characterization of thin polymer films will be accomplished using grazing incidence X-ray diffraction (GIXD), and charge delocalization will be probed using charge modulation spectroscopy (CMS) on oriented samples in order to obtain polarization resolution. The proposed activity will provide the organic electronics community with a method to experimentally and theoretically evaluate materials quickly for the design of high-performance organic semiconductors. It will also provide the first measurements of the coherence length of polarons in conjugated polymers using steady-state infra-red absorption spectroscopy. The coherence length will be linked to the design of new conjugated polymers and their short-range morphologies, thereby providing fundamental insights into what governs delocalization and trapping in conjugated polymer films.