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

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。它们在生物电子学中作为传感器或换能器的活性材料也有很大的潜力。所有这些装置都是通过输送电荷来工作的；因此，寻找具有大电荷迁移率的材料是有机电子学领域的主要目标。然而，对高迁移率有机半导体的探索，在很大程度上仍是在爱迪生哲学的指导下进行的。该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。从理论中获得的洞察力将用于设计和合成分子，这些分子将通过x射线衍射进行结构表征和光学光谱测量电荷离域进行实验分析。这些特性将与材料携带电流的能力相关。最终目标是将分子结构的特定特征和组装中分子的短程排列与载流子迁移率联系起来。所开发的方法，无论是理论还是实验，都有可能简化对高迁移率聚合物的寻找，并为下一代高性能有机电子设备铺平道路。技术概述功能材料的合理设计将基于一个理论模型，该模型考虑电荷输运、核电子耦合以及适合混合或分离pi-堆叠的二维晶格内对角线和非对角线无序的各种表现。从理论推导出的设计原则将在几个模型供体-受体共聚物上进行测试，其中链内扭转紊乱和/或HOMO能量交替被仔细控制。结构/性能关系将在基于吲哚二噻吩结构基序的高性能共聚物上进行评估，这些共聚物使用具有不同吸电子强度的受体。利用掠入射x射线衍射（GIXD）完成聚合物薄膜的微观结构表征，并利用电荷调制光谱（CMS）对取向样品进行电荷离域探测，以获得极化分辨率。提出的活动将为有机电子学社区提供一种快速实验和理论评估材料的方法，用于高性能有机半导体的设计。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。相干长度将与新共轭聚合物的设计及其短程形态联系起来，从而为共轭聚合物薄膜中的离域和捕获提供基本见解。

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.