Disentangling Relationships among Dopant Structure, Dopant and Polymer Energetics, Thin-Film Morphology, and the Electrical Properties of Doped Conducting Polymer Films

有机半导体有望实现新一代低成本、机械柔性和可穿戴电子设备。随着有机发光二极管（OLED）在手机、平板电脑显示器和电视上的广泛应用，它们的潜在用途才刚刚开始在商业规模上得到实现。此外，这些材料正在探索用于太阳能电池、电子电路、传感器和直接从溶液中打印的热电设备。在许多情况下，有机半导体在化学上掺杂了引入载流子的分子，以使材料更具导电性，这在许多应用中是可取的。例如，在OLED中使用化学掺杂来提高亮度和功率效率。提高掺杂有机半导体的性能和稳定性对其应用的电子器件的进一步发展至关重要，然而预测化学掺杂如何影响有机半导体的电子性能是极其困难的。本研究采用紧密结合的实验和理论方法来解开影响掺杂有机半导体电子特性的变量，目的是提高材料在多种潜在应用中的性能和稳定性。除了加速基于有机半导体的应用开发之外，该提案还旨在通过让整个肯塔基州的高中生接触有机半导体带来的激动人心的技术，促进对STEM学科的兴趣、参与和参与。在某种程度上，这个目标涉及到一个研讨会，让高中生制作电致变色装置，即通过电化学掺杂改变颜色的材料，以及热电装置，即材料收集热量并将其转化为电能，并了解计算化学的力量。由于多个变量的相互作用以及缺乏对每个变量如何影响材料性能的理解，掺杂有机半导体的电子和热电性能仍然非常难以预测。本研究旨在通过基于高度集成的实验和理论方法，通过改进其电子结构和输运特性的模型，推进掺杂有机半导体的最新技术。三个主要研究目标是确定掺杂尺寸对材料电子结构的影响，建立掺杂共轭聚合物的能量学和形态与掺杂尺寸和扩散之间的关键联系，确定掺杂共轭聚合物的电子结构和形态对热电应用感兴趣的材料的电导率和塞贝克系数的影响。研究方法包括在模型体系上应用紫外和逆光电子能谱，结合量子化学计算和分子动力学模拟来确定掺杂剂尺寸和聚合物形态对电子结构的影响。此外，电化学晶体管的电导率和塞贝克测量结合动力学蒙特卡罗模拟将揭示能量学和形态学如何影响电荷载流子输运和热电性能。本研究的总体目标是建立掺杂剂分子结构、有机半导体电子结构与掺杂有机半导体形态、电导率和塞贝克系数之间的明确关系。这些发现是实现具有受控电子特性的掺杂有机半导体更好的预测设计的关键。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。

Organic semiconductors promise to enable new generations of low-cost, mechanically flexible, and wearable electronic devices. Their potential uses are only beginning to be realized on the commercial scale with the recent widespread adoption of organic light emitting diodes (OLED) in cell phone and tablet displays and televisions. Further, these materials are being explored for use in solar cells, electronic circuitry, sensors, and thermoelectric devices that are printed directly from solution. In many cases, organic semiconductors are chemically doped with molecules that introduce charge carriers to make the materials more electrically conductive, as is desirable for many applications. For example, chemical doping is used in OLED to increase brightness and power efficiency. Improving the performance and stability of doped organic semiconductors is critical to the further development of electronic devices in which they may be used, yet it is extremely difficult to predict how a chemical dopant will affect the electronic properties of an organic semiconductor. This research uses a tightly integrated experimental and theoretical approach to disentangle variables that influence the electronic properties of doped organic semiconductors, with the goal of enhancing the material performance and stability across multiple potential applications. In addition to accelerating the development of applications based on organic semiconductors, the proposal aims to promote interest, engagement, and participation in STEM disciplines through exposing high school students throughout the state of Kentucky to the exciting technologies enabled by organic semiconductors. In part, this goal involves a workshop where high school students make electrochromic devices, where a material changes color through electrochemical doping, and thermoelectric devices, where a material harvests heat and turns it into electricity, and learn about the power of computational chemistry.The electronic and thermoelectric properties of doped organic semiconductors remain extremely difficult to predict due to the interplay of multiple variables and a lack of understanding of how each variable impacts the material properties. This research seeks to advance the state-of-the-art of doped organic semiconductors by refining models of their electronic structure and transport characteristics based on a highly integrated experimental and theoretical approach. The three primary research objectives are to determine the influence of the dopant size on the material electronic structure, establish critical connections between doped conjugated polymer energetics and morphology with dopant size and diffusion, and ascertain the influence of doped conjugated polymer electronic structure and morphology on the electrical conductivity and Seebeck coefficient of materials of interest for thermoelectric applications. The research approach involves application of ultraviolet and inverse photoelectron spectroscopy on model systems coupled with quantum-chemical calculations and molecular dynamics simulations to determine the influence of dopant size and polymer morphology on electronic structure. Furthermore, electrical conductivity and Seebeck measurements on electrochemical transistors combined with kinetic Monte Carlo simulations will uncover how energetics and morphology influence charge-carrier transport and thermoelectric performance. The overall objective of the research is to establish clear relationships between dopant molecular structure, organic semiconductor electronic structure, and doped organic semiconductor morphology, electrical conductivity, and the Seebeck coefficient. These findings are key to enable better predictive design of doped organic semiconductors with controlled electronic properties.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.