Uniform Self-Forming Metallic Network as a High-Performance Transparent Conductive Electrode
Uniform Self-Forming Metallic Network as a High-Performance Transparent Conductive Electrode
复制标题
均匀自形成金属网络作为高性能透明导电电极
DOI：
10.1002/adma.201302950
复制
发表时间：
2014-02-01
影响因子：
29.4
通讯作者：
Kempa, Krzysztof
中科院分区：
文献类型：
--
作者：
Han, Bing;Pei, Ke;Kempa, Krzysztof
同时具有高电导率和光学透射率的材料对于各种光电器件是必不可少的，例如触摸屏显示器，[1-4]太阳能电池[2，5-7]和有机发光二极管。[2，8，9]掺杂的金属氧化物膜，例如锡掺杂的氧化铟（ITO）和氟掺杂的氧化锡（FTO），已经主导了该领域[9，10]，但是具有几个关键的缺点，包括高价格、材料（例如铟）稀缺、高加工温度和脆性。[2，11]下一代光电器件需要透明导电电极，除了非常导电和透明之外，还具有机械柔性并与大规模制造兼容。[2，11]这些问题和要求促使人们寻找新材料。最近，纳米材料的发展，如碳纳米管，[1，8，12]石墨烯，[3，5，13]金属纳米线，[4，6，14，15]和金属网格[16，17]已经开辟了新的方向。其中，金属纳米线结合光电优势和低成本制造，包括滚-滚技术，[2，14，15]，[18]为ITO的替代开辟道路。许多团体的努力已经导致金属纳米线网络的性能的显著改善。特别地，银网络已经被提出用于触摸屏显示器[2，4]和光伏器件中的应用。[2，7，19]银金属网络通常从溶液中沉积为薄膜或网络以形成导电层。[6，7，14，19]最近，一些新的技术已经被开发出来来制造这些结构，例如气泡模板，[20]咖啡环效应模板，[21]在液体界面处的自组装，[22]等等。基于随机纳米颗粒和纳米线的溶液处理方法提供了一种廉价和灵活的方法来制造透明导电电极，但是仍然存在许多问题，例如光和电传导性之间的平衡、纳米颗粒/纳米线的均匀性及其在膜中的分布、纳米颗粒/纳米线本身之间以及金属网络和衬底之间的电接触。这些限制要求新的、改进的和可扩展的方法来制造金属网络膜。[2，15]在这项工作中，我们提出了一种新的方法-基于“破裂”的凝胶膜来制造金属网络-没有上述问题。将金属网络蒸发/溅射到自然破裂的凝胶膜的模板上。具有微米尺寸间距和银线的金属网络电极除了具有与ITO相当的透射率和较低的薄层电阻之外，还易于图案化并显示出对柔性基板的良好粘附性。图1示意性地示出了金属网络的制备过程，其主要包括四个步骤：TiO 2膜（作为模板膜）的合成和沉积、自开裂、金属膜沉积和模板膜剥离。凝胶膜、裂纹和金属网络的所得单个示意图也显示在图1的右侧。将微晶二氧化钛溶液的氧化物凝胶旋涂在玻璃或聚对苯二甲酸乙二酯（PET）基底上。采用溶胶-凝胶法制备了微晶TiO 2溶液。[23]在许多以前的应用中，TiO 2已被用作染料敏化太阳能电池的半导体层，[24，25]气体传感器，[26，27]等，但裂纹和分层经常在热处理过程中发展，[28]裂纹形成的机制已在其他地方详细说明。[29在这里，我们利用这个通常不需要的...
Materials with simultaneous high electrical conductivity and optical transmittance are essential for various optoelectronic devices, such as touch-screen displays,[1–4] solar cells,[2, 5–7] and organic light-emitting diodes.[2, 8, 9] Doped metal oxide films, such as tin-doped indium oxide (ITO) and fluorine-doped tin oxide (FTO), have dominated the field [9, 10] but suffer from several critical drawbacks, including high price, scarcity of materials (eg, indium), high processing temperatures, and brittleness.[2, 11] The next generation of optoelectronic devices requires transparent conductive electrodes, which in addition to being very conductive and transparent are also mechanically flexible and compatible with large-scale manufacturing.[2, 11] These problems and requirements motivate searches for new materials. Recently, development of nano-materials, such as carbon nanotubes,[1, 8, 12] graphene,[3, 5, 13] metal nanowires,[4, 6, 14, 15] and metal grids [16, 17] has opened new directions.Among these, metal nanowires combining optoelectronic advantages with low-cost manufacturing, including the roll-toroll techniques,[2, 14, 15, 18] lead the way for the ITO replacement. Efforts by many groups have led to significant improvements in the performance of metal nanowire networks. In particular, the silver networks have been proposed for applications in touch-screen displays [2, 4] and photovoltaic devices.[2, 7, 19] Silver metallic networks are normally deposited as a thin film or network from solution to form a conductive layer.[6, 7, 14, 19] Recently, some new techniques have been developed to fabricate these structures, such as the bubble template,[20] the coffee ring effect template,[21] self assembly at a liquid interface,[22] and so on. The solution-processed methods based on random nanoparticles and nanowires offer a cheap and flexible way to fabricate the transparent conductive electrodes, but many problems still remain, such as the balance between optical and electrical conductivity, uniformity of the nanoparticles/nanowires and their distribution in a film, and the electrical contact between the nanoparticles/nanowires themselves, as well as between the metallic network and a substrate. These limits call for new, improved, and scalable approaches to fabricate metallic network films.[2, 15] In this work, we propose a new approach—based on the “cracked” gel film for making metallic networks—free of the above problems. Metallic network is evaporated/sputtered onto a template of naturally cracked gel film. The metallic network electrodes with micrometer-size pitch and silver lines, in addition to having a comparable transmittance and lower sheet resistance than ITO, are also easy to pattern and show good adhesion to flexible substrates. Figure 1 schematically shows the processes of metallic network fabrication, which mainly includes four steps: synthesis and deposition of the TiO 2 film (as a template film), selfcracking, metallic film deposition, and template film lift-off. The resulted individual schematic images of the gel film, cracks, and the metallic network are also shown on the right side of Figure 1. An oxide gel of microcrystalline TiO 2 solution was spin-coated on a substrate of either glass or poly (ethylene terephthalate)(PET). The microcrystalline TiO 2 solution was synthesized by a normal sol-gel method.[23] In many previous applications, TiO 2 has been used as a semiconductor layer for dye-sensitized solar cells,[24, 25] gas sensors,[26, 27] and so on, but cracks and delamination often develop during thermal treatments,[28] and the mechanism of crack formation has been detailed elsewhere.[29, 30] Here, we take advantage of this normally unwanted …