银纳米线透明导电薄膜的失效机理研究

doi:10.15541/jim20190098

摘要/Abstract

摘要：

银纳米线透明导电薄膜材料作为新兴的无铟电极材料, 以其优越的光电性能和力学柔韧性, 在显示器件、触控面板、太阳能电池、智能加热和电磁屏蔽等领域崭露头角, 吸引越来越多的来自科研界及产业界的关注。然而, 银纳米线透明导电薄膜在应用中面临着较为严重的稳定性问题, 主要表现为容易被痕量含硫气体腐蚀, 在300 ℃以上的温度下纳米线出现断裂和球形化等结构失稳现象, 在紫外光照条件下腐蚀及球形化加剧, 在加载电场条件下出现离子迁移并产生孔洞及断裂现象。本文详细介绍了以上各种失效现象, 分析了失效的微观机制, 介绍了解决各种失效现象的具体措施。银纳米线透明导电薄膜失效行为的研究, 有助于进一步推动该材料的实际应用进程。

关键词: 银纳米线, 透明导电薄膜, 失效机理, 电迁移, 硫化, 综述

Abstract:

Silver nanowire transparent conductive film is one of the new indium-free electrode materials. It has attracted increasing attention from academia and industry due to its superior optoelectronic properties and excellent flexibility. It has been employed in a wide variety of applications in displays, touch panels, solar cells, smart heaters, electromagnetic interference shielding, and so on. However, silver nanowire transparent conductive film has a serious stability issue in service, for example, break or spheroidization above 300 ℃ under fulfidation, accelerating the degradation under ultraviolet light, pores for mation or even breakdown due to electromigration. In this review, the degradation phenomena is thoroughly introduced, the degradation mechanisms is analyzed, and the remedy strategy of degradation is discussed.

Key words: silver nanowires, transparent conductive films, degradation mechanism, electromigration, sulfidation, review

中图分类号:

TQ174

叶长辉, 顾瑜佳, 王贵欣, 毕丽丽. 银纳米线透明导电薄膜的失效机理研究[J]. 无机材料学报, 2019, 34(12): 1257-1264.

YE Chang-Hui, GU Yu-Jia, WANG Gui-Xin, BI Li-Li. Degradation Mechanism of Silver Nanowire Transparent Conductive Films: a Review[J]. Journal of Inorganic Materials, 2019, 34(12): 1257-1264.

图/表 8

图1 银纳米线的不同失效形式

Fig. 1 Different failure modes of silver nanowires (a) Chemical corrosion[10]; (b) Thermal failure[15]; (c) Joule heat failure[18]; (d) Electromigration[27]

图2 同一银纳米线样品在环境条件下放置不同时间的透射电镜照片[10]

Fig. 2 TEM images of the same AgNW sample stored for different time after exposure to air at ambient condtions[10] (a) The sample just after synthesis; (b) The sample stored for 3 w; (c-e) The sample stored for 4, 5, and 24 w, respectively; (f) High-resolution TEM image of one of the crystallites that compose the shell with inset showing to the FFT of the image

表1 图2(f)经傅立叶变换(FFT)后测量所得晶面间距和晶面夹角[10]

Table 1 Interplanar distances and angles between lattice planes from the FFT in Fig. 2(f)[10]

Parameters	Measured values	Theoretical values
d₍₀₁₃₎/nm	0.242	0.242
d₍₁₁₁₎/nm	0.305	0.308
${{d}_{(10\bar{2})}}/\text{nm}$	0.311	0.311
(013) ∠ (111)/(°)	49.1	50.0
(111) ∠ $(10\bar{2})$./(°)	79.2	79.4
$(10\bar{2})$.∠ (013)/(°)	51.7	50.6

图3 两根相邻银纳米线之间的连接示意图[12]

Fig. 3 Schematic representation of a junction between two adjacent AgNWs[12] (a) As-deposited junction; (b) Local sintering; (c) Initiation of the deterioration of the junction; (d) SEM image of a AgNW junction after thermal load just before the failure point; (e-g) SEM images of bare AgNW electrodes (e) Before annealing and after annealing for (f) 200 ℃, 20 min and (g) 380 ℃, 20 min[14]

图4 (a)电流通过两根银纳米线网络结点的有限元模拟[22]; (b,c)方阻为12 Ω/□的银纳米线电极持续流过电流密度为17 mA/cm2的电流17 d后的SEM照片[21]; (d~f)银纳米线网络在焦耳热作用下的SEM照片[22]: (d)银纳米线网络局部断裂; (e)热点的扩大; (f)热点合并, 形成电不连续区域

Fig. 4 (a) Finite-element simulation of the current flow through a two AgNW junction[22]; (b, c) SEM images of a 12 □/sq AgNW electrode under a constant current density of 17 mA/cm2 for 17 d [21]; (d-f) SEM image of AgNW network under Joule heating[22]: (d) Local fracture of the AgNW network; (e) Expansion of hot spots; (f) Hot spots merge to form an electrically discontinuous region

图5 光照后银纳米线上或周围出现的大、小颗粒的形貌图[23]

Fig. 5 The morphology of the small nanodots and large particles emerged on/around silver nanowires after light irradiation[23] (a) The small nanodots on/around single AgNW; (b) The small nanodots on/around AgNWs with different diameters; (c) The small nanodots at the end of AgNW and also the large particle at the wire-wire junction with inset showing the high magnification image; (d) The large particle adjoined AgNWs

图6 双晶银纳米线在54 mA电流下的SEM照片[26]

Fig. 6 SEM images of a bi-crystalline AgNW under a current of 54 mA[26] (a) Prior electrical stressing; (b-e) The direction of vacancy movement when the current flows to the left; (f-i) The direction of vacancy movement when the current moves to the right; (k-n) Surface morphology SEM images of the AgNW network in different stages of degradation[27]: (k) Fresh sample; (l) Degradation with larger grain size; (m) The emergence of larger voids; (n) Complete breakdown

图7 针对银纳米线的失效形式所提出的具体解决措施

Fig. 7 Remedy strategy of silver nanowire degradation (a) A self-assembled organic 2-mercaptobenzimidazole (MBI) used as an inhibitor of AgNWs[28]; (b) ZnO-AgNW composite electrode prepared by AP-SALD[12]

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