Structure–property investigations in urea tethered iodinated triphenylamines
Structure–property investigations in urea tethered iodinated triphenylamines
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尿素束缚的碘化三苯胺的结构和性质研究
DOI：
10.1039/d2cp01856j
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发表时间：
2022
影响因子：
3.3
通讯作者：
Shimizu, Linda S.
中科院分区：
文献类型：
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作者：
Hossain, Muhammad Saddam;Ahmed, Fiaz;Karakalos, Stavros G.;Smith, Mark D.;Pant, Namrata;Garashchuk, Sophya;Greytak, Andrew B.;Docampo, Pablo;Shimizu, Linda S.
在此，我们报告了尿素定向自组装碘化三苯胺（TPA）衍生物的结构、计算和电导率研究。尽管有大量关于导电 TPA 的报道，但将其固态组装与电荷传输特性关联起来的挑战阻碍了新材料的有效设计。在这项工作中，我们比较了二碘 TPA 的亚甲基脲桥联二聚体 (1) 和相应的亚甲基脲二碘 TPA 单体 (2) 与二碘单醛 (3) 对照的组装结构。这些修饰导致 1 和 2 形成针状晶体，这些晶体通过脲氢键、π⋯π 堆积、I⋯I 和 I⋯π 相互作用组织，如 SC-XRD、Hirshfeld 表面分析和 X 射线光电子能谱 (XPS) 所确定。长针状晶体足够坚固，可以通过两种接触探针方法测量电导率，其中 2 种表现出比 1 种（1.6 × 10−8 S cm-1）更高的电导率值（∼6 × 10−7 S cm−1）。在紫外线照射下，1 形成了少量的持久性自由基，而简单的甲基脲 2 显示出较少的自由基形成。使用价带 XPS 进一步研究了 1 的电子特性，结果显示在紫外线照射 (0.5-1.9 eV) 下价带发生显着变化，表明这些材料作为无掺杂 p 型空穴传输体的潜力。电子结构计算表明，TPA 的紧密堆积促进了它们的电子耦合并允许有效的载流子传输。我们的结果表明，离子添加剂显着提高了薄膜的电导率高达~2.0 × 10−6 S cm−1，使其能够在钙钛矿或固态染料敏化太阳能电池等功能器件中实现。
Herein, we report structural, computational, and conductivity studies on urea-directed self-assembled iodinated triphenylamine (TPA) derivatives. Despite numerous reports of conductive TPAs, the challenges of correlating their solid-state assembly with charge transport properties hinder the efficient design of new materials. In this work, we compare the assembled structures of a methylene urea bridged dimer of di-iodo TPA (1) and the corresponding methylene urea di-iodo TPA monomer (2) with a di-iodo mono aldehyde (3) control. These modifications lead to needle shaped crystals for 1 and 2 that are organized by urea hydrogen bonding, π⋯π stacking, I⋯I, and I⋯π interactions as determined by SC-XRD, Hirshfeld surface analysis, and X-ray photoelectron spectroscopy (XPS). The long needle shaped crystals were robust enough to measure the conductivity by two contact probe methods with 2 exhibiting higher conductivity values (∼6 × 10−7 S cm−1) compared to 1 (1.6 × 10−8 S cm−1). Upon UV-irradiation, 1 formed low quantities of persistent radicals with the simple methylurea 2 displaying less radical formation. The electronic properties of 1 were further investigated using valence band XPS, which revealed a significant shift in the valence band upon UV irradiation (0.5–1.9 eV), indicating the potential of these materials as dopant free p-type hole transporters. The electronic structure calculations suggest that the close packing of TPA promotes their electronic coupling and allows effective charge carrier transport. Our results show that ionic additives significantly improve the conductivity up to ∼2.0 × 10−6 S cm−1 in thin films, enabling their implementation in functional devices such as perovskite or solid-state dye sensitized solar cells.