Degradation of Organic Semiconductors: Functional and Mechanistic Descriptions from Macroscale to Nanoscale

能够导电的有机材料——被称为有机半导体——被用于许多新兴的下一代技术，包括有机发光二极管、有机太阳能电池、热电器件和化学传感器。有机半导体的优点包括成本更低、性能更好、灵活性、透明度和对环境的影响更小，但对其长期稳定性和使用寿命的担忧仍然存在。本项目的重点是功能特性的退化，这是有机电子器件领域必须克服的基本材料化学挑战。在材料研究部固态和材料化学项目的支持下，研究人员在基础水平上推进了对材料和化学降解途径的理解，这将最终促进新材料设计标准的发展。因此，这项工作提供了重要的新见解，推动了新分子和聚合物的创造，并有助于美国在可印刷电子材料和设备方面的长期稳定性和技术相关性。固态和材料化学项目的支持也推动了有机半导体系统的独特功能的发展，这些功能很容易转化为其他活性材料化学应用，并能够识别从微米到纳米尺度上伴随材料降解的化学途径。化学家和工程师之间的跨学科努力为从事研究的研究生和本科生提供了跨学科培训的平台。通过这一努力，新的跨学科研究生和本科水平的实验室经验得到了发展，这类重要材料的特性在K-to-gray公共推广工作中得到了探索。推挽式或供体-受体型分子和聚合物结构已成为有机电子领域活性材料的主导类别，其性能指标优于早期的分子设计。然而，很少有人关注对长期稳定性的理解。这项基础性工作直接考察和比较了复杂的推拉式有机半导体（OSC）结构的化学结构、电子结构和电荷输运特性，并将其作为分子构建块组成的函数，以了解降解的化学、光化学和光物理机制起源和功能影响。这项工作的第二个影响是为更健壮的osc制定了新的设计标准。这项工作建立在通过以前的NSF DMR奖（DMR-1608289）的成功努力的基础上，其中发起了有机半导体降解的协作，多学科研究。先前演示的方法包括在导致降解的条件下测量功能特征，再加上详细的光谱分析方法来了解机械分子起源。在这个项目中，能力被扩展到包括具有特定位点的分子和电子成像能力的局部物理结构，从而能够在从微米到纳米的长度尺度上研究基础材料化学。除了改进新兴技术的材料设计外，这项工作的广泛影响还体现在许多教育和推广活动中。化学家和工程师之间的合作为从事研究的研究生和本科生提供了跨学科培训的平台。通过这一努力，新的跨学科研究生和本科水平的实验室经验得到了发展，这类重要材料的性质和用途在K-to-gray推广工作中得到了解释和探索。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical AbstractOrganic materials capable of conducting electricity – termed organic semiconductors - are used in many emerging, next-generation technologies including organic light emitting diodes, organic-based solar cells, thermoelectrics, and chemical sensors. The benefits of organic semiconductors include lower cost, improved performance, flexibility, transparency, and lower environmental impact, but concerns persist about their long-term stability and lifetime. The focus of this project – degradation of functional properties – is a fundamental materials chemistry challenge that must be overcome to progress the field of organic electronic devices. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, the researchers advance the understanding of materials and chemical degradation pathways at a fundamental level, which will eventually facilitate development of new materials design criteria. Hence, this work provides important new insights that drive the creation of new molecules and polymers and contributes to long-term stability and technological relevance of the United States in printable electronic materials and devices. Support from the Solid State and Materials Chemistry program also advances the development of unique capabilities for in operando characterization of organic semiconductor systems that are readily translatable to other active materials chemistry applications and enable identification of the chemical pathways that accompany degradation in materials at length scales from microns to nanometers. This inherently interdisciplinary effort between chemists and engineers is a platform for interdisciplinary training for the graduate and undergraduate students engaged in research. New interdisciplinary graduate- and undergraduate-level laboratory experiences are developed through this effort, and the properties of this important class of materials are explored in K-to-gray public outreach efforts. Technical AbstractPush-pull or donor-acceptor-type molecular and polymeric architectures have become the dominant class of active materials in organic electronics with performance metrics superior to earlier molecular designs. However, little attention has been devoted to understanding long-term stability. This fundamental effort directly examines and compares chemical structure, electronic structure, and charge transport characteristics of complex push-pull organic semiconductor (OSC) architectures as a function of molecular building block composition to understand the chemical, photochemical and photophysical mechanistic origins and functional impacts of degradation. The secondary impact of this effort is formulation of new design criteria for more robust OSCs. This work builds on successful efforts through a previous NSF DMR award (DMR-1608289) in which a collaborative, multi-disciplinary investigation of organic semiconductor degradation was initiated. Previously-demonstrated approaches include surveying functional characteristics under conditions that lead to degradation, coupled with detailed spectroscopic analysis methodologies to understand mechanistic molecular origins. In this project, capabilities are expanded to include local physical structure with site-specific molecular and electronic imaging capabilities, which enables investigation of fundamental materials chemistry across length scales ranging from microns to nanometers. In addition to improving materials design for emerging technologies, the broader impacts of this work manifests through numerous education and outreach activities This collaboration between chemists and engineers is a platform for interdisciplinary training for the graduate and undergraduate students engaged in research. New interdisciplinary graduate- and undergraduate-level laboratory experiences are developed through this effort, and the properties and uses of this important class of materials are explained and explored in K-to-gray outreach efforts.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.