自修复有机分子整流器的设计合成与性能研究

One of the factors that hamper the development of organic/molecular electronic devices is the poor electrical performance in terms of stability and reproducibility due to the nature that organic molecules are not as stable as inorganic crystal, i.e. silicon. For molecular electronics to continue to evolve, it is important to demonstrate good electronic performance with alternative design strategy. Inspired by the mechanism of self-healing materials, we for the first time introduce by tuning molecule/molecule interactions to achieve the self-healing of electronic performance to overcome the bottle neck of the stability and reproducibility problem in molecular electronics. Here, we designed a series of self-assembled monolayers (SAMs) based molecular diodes that contains electron donor (D) ferrocene (Fc) terminal groups separated by fully saturated molecular bridge (b) from the electron acceptor aromatic rings (Ar) as the conjugated backbone, to generate D-b-A molecular architecture. We abbreviate these types of molecular diodes as Fc-Ar. The supramolecular structure and the self-healing property of the SAMs can be controlled by different chemical modifications of backbone to create intermolecular interactions such as π-π stacking, hydrogen bond and covalent bond. To demonstrate the self-healing of molecular rectification, we fabricate the molecular junctions with different platform including conductive probe atomic force microscopy (cpAFM) and liquid metal EGaIn (Ga and In alloy) setup. The aim of this work is to reveal the role of the intermolecular interactions in the self-healing of the supramolecular structure and to benefit from the self-healing property of the SAMs to the electronic performance of the molecular diodes, in terms of high rectification ratio, reproducibility, long stability. We believe that our work is an important step forward in the continuous process of unravelling the design rules and directions of high performance functional molecular electronic devices with complex structure.

分子器件的稳定性是目前分子电子学中亟待解决的难题之一，近几年利用分子间作用力进行材料自修复的研究成果启发了分子器件设计革命性的理念创新，即利用自修复机制来突破分子器件不稳定的瓶颈。本项目设计了一系列由二茂铁氧化还原基团（Fc）和芳香共轭骨架（Ar）构成的线型有机分子，利用分子骨架间π-π stacking、氢键、共价键等作用力方式调控分子的自组装行为，并考察分子间作用力对自组装单分子膜超分子结构和自修复能力的影响。利用导电AFM和微流体EGaIn电极等技术构筑“金属/有机分子/金属”分子结研究自组装单分子膜的整流特性，揭示 “分子间作用力-自修复能力-整流特性” 之间的相互关系，探讨该类分子形成整流的机制以及自修复能力对整流特性的影响，制备具有高稳定性和自修复能力的分子整流器。本项目对未来分子逻辑电路的设计，构筑复杂的分子器件具有重大意义。

构筑高稳定、长寿命、可自修复的分子器件是目前分子电子学面临的一个重要挑战。本项目使用液态镓铟合金制备微尺度电极，构筑了一系列金属//有机分子//金属的分子结，并成功的用于自组装单分子薄膜电学特性的研究，取得了以下结果：1）在组氨酸修饰的寡聚丙氨酸多肽链中，通过改变组氨酸修饰位点实现了肽链电荷输运能力的精细调控；2）在一类具有整流特性的exTTF衍生物中，对具有氧化还原反应的exTTF基团进行化学修饰，调整分子的能级位置，实现了分子整流器阈值电压的精细调制；3）设计了一系列具有“烷基链-联苯”骨架的二茂铁衍生物，发现这类刚柔相间的分子骨架在单分子薄膜中表现出类似液晶的特性，通过电场诱导实现了分子的规则排列，提高了分子器件的电学性能，并构筑了电场驱动的自修复分子整流器件；4）通过分子间氢键形成位点的设计，调控TTF衍生物的自组装行为，制备了TTF衍生物的致密组装薄膜，并将该类薄膜应用于有机太阳能电池的空穴传输修饰层，有效提高了器件的光电转化效率。