Molecular Doping of Semiconducting Polymers

摘要非技术功能电子产品可以用聚合物制成，用于可穿戴电子产品和太阳能电池等应用。电子聚合物可以像墨水一样被涂覆或印刷，以在塑料甚至可拉伸材料上制造设备。这些电子聚合物的导电性可以通过添加称为掺杂剂的材料来控制。掺杂剂的有效性取决于电荷如何转移到电子聚合物中，以及可以结合多少电荷。该项目由美国国家科学基金会材料研究部的固体与材料化学计划和聚合物计划共同支持，加州大学圣巴巴拉分校(UCSB)的研究人员使用传输和先进的结构分析方法，如国家用户设施的X射线散射，研究了电子聚合物在掺杂过程中的结构和电子变化。他们还研究了机械效应，如弯曲或拉伸，如何影响掺杂到电子聚合物中。电子聚合物的这项研究致力于设计新材料，以制造与电子以及能量转换和存储相关的低成本电子设备，所获得的基本见解有望转化为一般的固态有机材料。该项目通过结合协作工作的电子材料方面的高级研究，帮助培养一批在美国STEM劳动力市场就业的不同类型的研究生。参与这项研究的本科生研究人员将接触到材料科学前沿的未来职业道路，包括毕业学习的道路。技术总结控制固态半导体聚合物的电掺杂需要注意能量和结构无序。该项目由固态和材料化学计划和聚合物计划联合支持，使UCSB的研究人员能够设计新的分子掺杂剂，从而能够控制半导体聚合物中掺杂的能量分布。掺杂剂基于稳定的有机自由基阳离子，这些阳离子具有适当的电离能，可以选择性地掺杂高性能半导体聚合物。这些掺杂剂可以调节给定半导体聚合物的电荷转移能量。掺杂剂还能够研究半导体聚合物纳米结构中掺杂剂位置的时间演变。掺杂电子聚合物的结构演变是通过先进的X射线散射方法和对掺杂剂化学结构敏感的电子显微镜相结合的方式来研究的。然后通过系统地研究掺杂过程中电子态密度随机械力的变化，揭示了半导体聚合物的机械应力与掺杂之间的耦合。静态掺杂和电化学掺杂的比较为进一步研究电子行为作为结晶度和机械行为的函数提供了一种手段。参与研究的研究生获得了多学科研究的技能，包括数据科学工具。研究成果通过同行评议期刊上的出版物向公众传播，数据可通过在线数据档案获得。该奖项反映了NSF的法定使命，并通过使用基金会的智力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 SUMMARYFunctional electronics can be made with polymers for applications including wearable electronics and solar cells. Electronic polymers can be coated or printed, like an ink, to make devices on plastics or even stretchable materials. The electrical conductivity of these electronic polymers can be controlled through the addition of materials called dopants. The effectiveness of dopants depends how charges are transferred to the electronic polymer and how many of them can be incorporated. For this project, which is jointly supported by the Solid State and Materials Chemistry Program and the Polymers Program, both in NSF’s Division of Materials Research, researchers at the University of California Santa Barbara (UCSB) study the structural and electronic changes of electronic polymers during doping using both transport and advanced structural analysis methods, such as X-ray scattering at national user facilities. They also investigate how mechanical effects, such as bending or stretching, impact the incorporation of dopants into electronic polymers. This research in electronic polymers addresses the design of new materials towards the manufacturing of low-cost electronic devices relevant for electronics and energy conversion and storage, and the fundamental insights gained are expected to be transferrable to solid-state organic materials in general. The project helps train a diverse set of graduate students for careers in the US STEM workforce through advanced research in electronic materials that incorporates collaborative work. Undergraduate researchers involved in the research are exposed to future career pathways at the forefront of materials science including pathways to graduate study. TECHNICAL SUMMARYControlling electrical doping of semiconducting polymers in the solid state requires attention to energetic and structural disorder. This project, which is jointly supported by the Solid State and Materials Chemistry Program and the Polymers Program, enables researchers at UCSB to design new molecular dopants that provide the ability to control the energetic distribution of doping within semiconducting polymers. The dopants are based on stable organic radical cations that have appropriate ionization energies to selectively dope high performance semiconducting polymers. These dopants allow tuning of the energetics of charge transfer for a given semiconducting polymer. The dopants further enable the investigation of the temporal evolution of the location of dopants within the nanostructure of semiconducting polymers. The structural evolution of doped electronic polymers is interrogated by a combination of advanced X-ray scattering methods and electron microscopy that are sensitive to the chemical structure of the dopant. The coupling between mechanical stress and doping of semiconducting polymers is then revealed by the systematic study of changes in the electronic density of states as a function of mechanical forces during doping. The comparison of both static and electrochemical doping provides a means to further examine the evolution of electronic behavior as a function of crystallinity and mechanical behavior. Graduate students involved in the research gain skills in multidisciplinary research including data science tools. The research outcomes are disseminated to the public through publications in peer-reviewed journals and the data is available through online data archives.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.