甲酸铜墨水低温钎焊铜纳米线的机理研究及其在透明电极中的应用

Flexible electronic is an important development tendency of technology in the future. Traditional indium tin oxide (ITO) transparent electrodes could not meet the requirements of flexible electronics, copper nanowire is a powerful candidate for ITO by virtue of excellent conductivity and flexibility. However, the processing temperature for copper nanowire transparent electrodes by reported methods were too high hindering their application on flexible polymer substrates. In this project, copper formate ink will be used as solders to join copper nanowires at low temperatures (<200℃), the effect of surfactant on copper nanowires, composition of copper formate ink, sintering parameters on the phase, morphology and microstructure of nanojoints will be studied, the nanosoldering mechanism will be revealed. The soldering technique will be used to fabricate copper nanowire transparent electrodes on various flexible substrates, the influence rule of nanosoldering by copper formate on the transmittance and sheet resistance of transparent electrodes will be discussed. Furthermore, the soldering process of copper nanowires by copper formate under air atmosphere will be operated in which organic solvent will be used to protect copper nanowires from being oxidized and the soldering mechanism in solvernt also will be discussed. This project will study soldering mechanism on nanoscale, provide data support for nanojoining and promote the development of flexible electronics.

柔性电子是未来科技发展的重要方向，传统的氧化铟锡(ITO)透明电极不能满足柔性化要求，铜纳米线凭借着优异的导电性和柔韧性成为替代ITO的有力候选材料。现有的铜纳米线透明电极制备技术存在加工温度高的问题，这极大限制了其在树脂基柔性基底上的应用。本项目使用甲酸铜墨水在氮气氛围中低温(<200℃)钎焊铜纳米线，研究铜纳米线表面基团、墨水成分、烧结工艺对连接接头的成分、形貌、微观结构的影响，揭示纳米钎焊的机理，并将这种钎焊技术应用于透明电极的制备，同时分析甲酸铜钎焊对铜纳米线透明电极透过率和方阻的影响规律，实现在多种柔性基底上制备铜纳米线透明电极。此外，将在空气氛围中进行甲酸铜钎焊铜纳米线的实验，使用有机溶剂保护铜纳米线不受氧气侵蚀，研究溶液中甲酸铜墨水的钎焊机制。本项目将钎焊技术应用于纳米尺度，为纳米连接提供数据支持，推进了透明电极的柔性化进程和柔性电子技术的发展。

透明电极是触摸屏、显示屏、太阳能电池等器件中的重要组元，传统的氧化铟锡(ITO)透明电极存在价格高、脆性大等缺陷，铜纳米线由于其优异的导电性和柔韧性成为替代ITO的有力候选材料。现有的铜纳米线透明电极加工技术存在加工温度高的问题，这极大限制了在树脂基柔性基底上的应用。原项目计划采用甲酸铜钎焊铜纳米线制作透明电极，研究纳米钎焊的机理。经过初步研究，本项目遇到了一些意想不到的现象，由于铜纳米线尺寸较小，溶解甲酸铜的2-氨基-2-甲基-1-丙醇有机溶剂会腐蚀纳米线，破坏整个导电网络导致实验失败。所以我们调整项目为使用表面涂覆纳米颗粒的热敏薄膜，避免在后期处理中的高温对基底透明度的影响。本项目使用光烧结技术在表面涂覆纳米颗粒的柔性聚对苯二甲酸乙二醇酯(polyethylene terephthalate, PET)基底上制作铜纳米线透明电极，研究了表面覆盖纳米颗粒的PET(surface coated PET, C-PET)和未覆盖纳米颗粒的PET(normal PET, N-PET)热性能对铜纳米线透明电极在光烧结前后电性能、透过率的变化规律，揭示了电性能和透过率改变机制，实现了可循环弯曲的透明电极制作。实验结果表明，铜纳米线在光烧结过程中形成了纳米连接，在透过率为82%的时候方阻低至33.3Ohm/sq。表面涂覆的纳米颗粒保护了C-PET在光烧结过程中的损伤，有利于形成高透过率的透明电极。本项目为在柔性热敏基底上制作铜纳米线透明电极提供了新的思路，推进了透明电极柔性化的发展。