Methods to Mitigate Dopant-Induced Disorder in Organic Electronic Materials

有机半导体是一种很有前途的低成本柔性电子材料。它们的导电性可以通过添加正电荷或负电荷来提高，这一过程被称为分子掺杂。然而，有机半导体中相反电荷之间的吸引力比硅等传统半导体更强。这会限制电荷传输，降低器件性能。这个项目的目标是确定可以削弱相反电荷之间吸引力的物理性质。pi将结合实验和模拟来了解哪些实验参数影响电荷输运。这些研究是实现太阳能电池、发光二极管、晶体管和传感器等高效、低成本有机电子产品的重要步骤。这项工作将培养学生在跨学科和融合材料研究的前沿，将实验与计算相结合。K-12和本科学生将被引入材料科学，pi将创建在线教育模块，向学生教授数值模拟。技术概述：为了提高有机半导体的导电性，需要掺杂。然而，掺杂对电荷通过载流子和电离掺杂之间的库仑相互作用进行输运产生不利影响，而有机材料的低介电常数很难屏蔽这种影响。该项目的目标是在不需要额外的合成修饰的情况下，确定介电筛选、离子-大分子相互作用和掺杂剂分布等特性对广泛共轭聚合物中掺杂剂诱导的能量紊乱的影响。这些研究验证了可以通过降低掺杂剂与聚合物之间的库仑相互作用来减少掺杂剂引起的能量紊乱的假设。研究人员将在广泛的载流子浓度范围内测量两个互补的电荷传输参数，塞贝克系数和电导率，并开发声子辅助跳跃模型来生成电子态密度图。这种结合实验计算的方法使研究人员能够提取载流子迁移率，并将掺杂剂引起的能量紊乱与电荷输运联系起来。研究人员将空间电荷限制电流和Mott-Schottky测量数据与电导率相结合，以验证计算的迁移率。这些研究代表了掺杂共轭聚合物中电荷输运的物理解释向前迈出的重要和变革性的一步，并提供了改善其性能的结构设计标准。研究人员正在培训和指导多样化的下一代化学家和材料科学家，开展外展活动，向不同层次的学生介绍材料科学，并在网上传播跳跃运输模拟工具。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。

NONTECHNICAL SUMMARYOrganic semiconductors are promising materials for low cost, flexible electronics. Their electrical conductivity can be increased by adding positive or negative charges, a process known as molecular doping. However, the attraction between the opposite charges in organic semiconductors is stronger than in conventional semiconductors such as silicon. This can limit charge transport and reduce device performance. The goal of this project is to identify the physical properties that can weaken the attraction between the opposite charges. The PIs will combine experiments with simulation to understand which experimental parameters impact charge transport. These studies are important steps for realizing efficient and low-cost organic electronics such as solar cells, light-emitting diodes, transistors, and sensors. This work will train students at the frontiers of interdisciplinary and convergent materials research that combines experiments with computation. K-12 and undergraduate students will be introduced to materials science and the PIs will create on-line educational modules to teach numerical simulation to students.TECHNICAL SUMMARYDoping is required to raise the conductivity of organic semiconductors. However, doping adversely impacts charge transport through Coulomb interactions between charge carriers and ionized dopants, which are poorly screened by the low dielectric constants of organic materials. The goal of this project is to determine the influence of properties such as dielectric screening, ion-macromolecular interaction, and dopant distribution on the dopant-induced energetic disorder in a wide range of conjugated polymers without the need for additional synthetic modification. These studies test the hypothesis that the dopant-induced energetic disorder can be reduced by decreasing the Coulomb interaction between the dopant and the polymer. The investigators will measure two complementary charge transport parameters, the Seebeck coefficient and electrical conductivity, over a broad range of carrier concentrations and develop phonon-assisted hopping model to generate maps of the electronic density of states. This combined experimental-computation approach allows the investigators to extract carrier mobility and correlate dopant-induced energetic disorder with charge transport. The investigators combine space-charge limited current and Mott-Schottky measurements data with conductivity to validate the calculated mobility. These studies represent a significant and transformative step forward in the physical explanation of charge transport in doped conjugated polymers and providing structural design criteria to improve their performance. The investigators are training and mentoring a diverse next generation of chemists and materials scientists, performing outreach activities to introduce materials science to students across levels, and disseminating the hopping transport simulation tool on-line.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.