Collaborative Research: Tuneable cross-conjugated organic semiconductors

波士顿大学的Malika Jeffries-El教授和北乔治亚大学的Aimee Tomlinson教授在化学系高分子、超分子和纳米化学(MSN)计划的支持下，开发了新的碳基材料-有机半导体-将有机材料的特性与传统无机半导体的光学和电子特性相结合。这些复杂的材料具有重要的技术意义，因为它们可以被制成各种不同领域的设备，包括能源(太阳能电池)、显示器(发光二极管)和电子设备(场效应晶体管)。在这个项目的过程中，Tomlinson的团队使用计算方法设计了基于类十字基序的共轭材料，以确定最有希望由Jeffries-EL小组合成和表征的候选材料。这项研究加深了我们对结构如何影响其材料性能，以及这些性能如何影响其在各种应用中的性能的理解。除了支持基础研究，这项资助还为本科生和研究生提供跨学科的研究经验。这笔赠款的更广泛影响包括培养高素质的科学家，他们在不同的环境中从事复杂的跨学科项目具有丰富的经验。由于北乔治亚大学位于蓝岭山脉的山脚下，许多第一代本科生和代表不足的本科生有机会参与这一项目。此外，Jeffries-El博士通过针对9-12年级低收入和低代表少数族裔学生的成就、自我意识、沟通、参与、网络和发展技能(ASCEND)推广计划，培养未被充分代表的高中生对材料化学的兴趣。该项目通过研究交叉共轭苯并双恶唑(BBOS)的结构-性质-形态关系，进一步推动了有机半导体领域的发展。交叉共轭分子是具有两条通过中心芳环相交的正交共轭路径的体系，由于这种排列导致了前线分子轨道(FMO)的空间分离，因此对于有机半导体应用特别有利。因此，由于PI体系的扩展和诱导效应，可以通过沿着不同轴的芳基取代来选择性地调节FMO和带隙。这种方法的好处是，交叉共轭平台允许有机会针对特定应用优化材料的光学和电子性能。根据前一次赠款期间的见解，有几个机会可以合理设计新材料，特别是用于光伏电池的窄带隙材料和可用作蓝色发光体或有机发光二极管主体的宽带隙材料的结构。利用理论、合成、器件制造和表征相结合的方法来识别和生成新材料，并为如何设计未来的材料提供见解。简单的迭代方法允许容易地合成目标材料，结构-性能研究促进了具有可调和可预测特性的新材料的合理设计。因此，这项工作预计将影响有机电子学领域。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professors Malika Jeffries-EL of Boston University and Aimee Tomlinson of University of North Georgia are supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to develop new carbon-based materials - organic semiconductors - that combine the properties of organic materials with the optical and electronic properties of conventional inorganic semiconductors. These complex materials are of technological importance as they can be fabricated into devices for use in a variety of different areas including energy (solar cells), displays, (light emitting diodes), and electronics (field effect transistors). During the course of this project, conjugated materials based on the cross-like motif are designed by Tomlinson's team using computational methods in order to identify the most promising candidates for synthesis and characterization by the Jeffries-EL group. This research enhances our understanding of how structure impacts its material properties, and how these properties then impact its performance in various applications. In addition to supporting basic research, this grant provides interdisciplinary research experiences for both undergraduate and graduate students. The broader impacts of this grant include the development of highly qualified scientists with extensive experience working on complex interdisciplinary projects in a diverse environment. Since the University of North Georgia is located in the foothills of the Blue Ridge mountain range a number of first generation and underrepresented undergraduates are given the opportunity to be involved in this project. Additionally, Dr. Jeffries-EL fosters interest in materials chemistry in underrepresented high school students through the Achievement, Self-Awareness, Communication, Engagement, Networking and Developmental Skills (ASCEND) outreach program targeting low-income and underrepresented minority students in grades 9-12. The project further advances the field of organic semiconductors through an investigation of structure-property-morphology relationships in cross-conjugated benzobisoxazoles (BBOs). Cross-conjugated molecules, which are systems with two orthogonal conjugation paths that intersect through a central aromatic ring, are especially advantageous for organic semiconducting applications as this arrangement leads to spatial segregation of the frontier molecular orbitals (FMOs). Consequently, it is possible to selectively tune the FMOs and band gaps through aryl group substitution along the various axes as a result of extension of the pi system and inductive effects. The benefits of the approach are that the cross-conjugated platform allows for the opportunity to optimize the material's optical and electronic properties for specific applications. Based on the insights from the previous grant period, there are several opportunities for the rational design of new materials, specifically architectures for narrow band-gap materials for photovoltaic cells and wide band gap materials which can be used as either blue emitters or hosts in organic light emitting diodes. A combination of theory, synthesis, device fabrication and characterization are utilized to identify and generate new materials as well as provide insights on how to design future materials. The simple iterative approach allows for easy synthesis of the target materials and structure-property studies advance the rational design of new materials with characteristics that are tunable and predictable. As such this work is expected to impact the field of organic electronics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.