Powell Daniel, Zhang Xueqiao, Nwachukwu Chideraa I, Miller Edwin J, Hansen Kameron R, Flannery Laura, Ogle Jonathan, Berzansky Alex, Labram John G, Roberts Andrew G, Whittaker-Brooks Luisa
Department of Chemistry, University of Utah, Salt Lake City, UT, 84112, USA.
School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR, 97331, USA.
Adv Mater. 2022 Oct;34(42):e2204656. doi: 10.1002/adma.202204656. Epub 2022 Sep 20.
Self-doping is a particular doping method that has been applied to a wide range of organic semiconductors. However, there is a lack of understanding regarding the relationship between dopant structure and function. A structurally diverse series of self-n-doped perylene diimides (PDIs) is investigated to study the impact of steric encumbrance, counterion selection, and dopant/PDI tether distance on functional parameters such as doping, stability, morphology, and charge-carrier mobility. The studies show that self-n-doping is best enabled by the use of sterically encumbered ammoniums with short tethers and Lewis basic counterions. Additionally, water is found to inhibit doping, which concludes that thermal degradation is merely a phenomenological feature of certain dopants, and that residual solvent evaporation is the primary driver of thermally activated doping. In situ grazing-incidence wide-angle X-ray scattering studies show that sample annealing increases the π-π stacking distance and shrinks grain boundaries for improved long-range ordering. These features are then correlated to contactless carrier-mobility measurements with time-resolved microwave conductivity before and after thermal annealing. The collective relationships between structural features and functionality are finally used to establish explicit self-n-dopant design principles for the future design of materials with improved functionality.
自掺杂是一种已应用于多种有机半导体的特殊掺杂方法。然而，对于掺杂剂结构与功能之间的关系尚缺乏了解。研究了一系列结构多样的自n型掺杂苝二亚胺（PDI），以研究空间位阻、抗衡离子选择以及掺杂剂/PDI连接距离对诸如掺杂、稳定性、形态和电荷载流子迁移率等功能参数的影响。研究表明，使用具有短连接基团的空间位阻铵和路易斯碱性抗衡离子最有利于实现自n型掺杂。此外，发现水会抑制掺杂，这表明热降解仅仅是某些掺杂剂的一种现象学特征，而残余溶剂蒸发是热激活掺杂的主要驱动力。原位掠入射广角X射线散射研究表明，样品退火会增加π-π堆积距离并缩小晶界，以改善长程有序性。然后将这些特征与热退火前后通过时间分辨微波电导率进行的非接触载流子迁移率测量相关联。结构特征与功能之间的总体关系最终被用于建立明确的自n型掺杂剂设计原则，以用于未来设计具有改进功能的材料。
