CAREER: Mechanical Behavior of Flexible Electronic Films

学院早期职业发展(Career)奖助金的目的是提高对有机(聚合物)半导体薄膜机械行为的理解。深入了解机械和电气性能之间的关系将为实现机械坚固的柔性电子产品提供指导，用于可穿戴电子产品和低成本太阳能等应用。有机半导体由于其分子结构的相对顺应性，在柔性电子产品中特别有希望。使用中的机械故障，主要是由于反复弯曲，阻碍了有机薄膜在灵活的电子应用中的商业应用。该奖项为研究分子结构、薄膜微结构和器件设计对器件在弯曲下的性能变化和失效模式的影响提供了支持。研究还将包括循环弯曲和环境因素(如湿度)对机械稳定性的影响。这项研究跨越了材料力学、材料加工和半导体器件物理等多个学科，将为学生提供一个激励的训练环境。该教育计划包括开发新兴薄膜电子制造和机械方面的证书课程，以培养这一新兴领域的未来领导者。研究目标将通过下列相互关联的任务来实现：(1)确定分子结构和分子堆积特征对共轭聚合物薄膜力学行为的影响；(2)确定多组分聚合物共混物的形态对电和机械响应的影响；(3)表征非均质薄膜中的界面特征，从而减少分层和粘合失效模式；(4)确定在各种加载协议和环境条件下在亚临界机械载荷下驱动性能变化和退化的特征，以及(5)开发柔性电子学的标准化力学测试方法。重点将放在有机薄膜晶体管和有机光伏器件上，它们捕捉到独特和基本的操作特性，以便研究产品可以在广泛的设备平台上进行推断。感兴趣的机械性能包括薄膜硬度、延展性、断裂强度以及内聚力和粘结力断裂能，这些将使用四点弯曲、双悬臂梁测试和屈曲计量法进行测量。拟议研究的智力价值体现在将聚合物半导体结构与机械和光电特性相联系的基本框架的开发中，从而使层状有机和有机-无机系统具有机械性能。

The objective of this Faculty Early Career Development (CAREER) grant is to improve the understanding of the mechanical behavior of organic (polymeric) semiconductor films. Insight into the relationships between mechanical and electrical properties will provide guidelines to achieve mechanically robust flexible electronics for applications such as wearable electronics and low cost solar energy. Organic semiconductors are particularly promising for flexible electronics due to their relatively compliant nature associated with their molecular structure. Mechanical failure in use, primarily due to repeated flexing, has hindered the commercial adoption of organic films for flexible electronic applications. This award provides support to investigate the impact of molecular structure, film microstructure, and device design on performance variation and failure modes of devices under flexure. Research will also include the role of cyclic bending and environmental factors such as moisture on mechanical stability. This research crosses multiple disciplines including mechanics of materials, materials processing, and semiconductor device physics and will provide a stimulating training environment for students. The education plan includes the development of a certificate program in manufacturing and mechanics of emerging thin film electronics to train future leaders in this emerging field. The research objectives will be addressed through the following interrelated tasks: (i) determining the effect of molecular structure and molecular packing characteristics on the mechanical behavior of conjugated polymer films, (ii) establishing the impact of multi-component polymer blend morphology on electrical and mechanical response, (iii) characterizing interfacial features in heterogeneous films, such that delamination and cohesive failure modes can be mitigated, (iv) determining the features that drive performance variation and degradation under sub-critical mechanical loading under various loading protocols and environmental conditions, and (v) developing standardized mechanical test methods for flexible electronics. A focus will be on organic thin film transistors and organic photovoltaic devices that capture unique and fundamental operating characteristics so that the research products may be extrapolated across broad device platforms. Mechanical properties of interest include film stiffness, ductility, fracture strength, and cohesive and adhesive fracture energy that will be measured using four-point bending, double cantilever beam testing, and buckling metrology methods. The intellectual merit of the proposed research is found in the development of a fundamental framework relating polymer semiconductor structure to mechanical and optoelectronic characteristics enabling mechanically robust layered organic and organic-inorganic systems.