Buckling Instability Control of 1D Nanowire Networks for a Large‐Area Stretchable and Transparent Electrode

Abstract

A commonly used strategy to impose deformability on conductive materials is the prestrain method, in which conductive materials are placed on prestretched elastic substrates and relaxed to create wavy or wrinkled structures. However, 1D metallic nanowire (NW) networks typically result in out-of-plane buckling defects and NW fractures, due to their rigid and brittle nature and nonuniform load transfer to specific points of NW. To resolve these problems, an alternative method is proposed to control the elastic modulus of 1D NW networks through contact with various solvents during compressive strain. Through solvent contact, the interface interactions between the NWs and between the NW and substrate can be controlled, and it is shown that the surface instability of the 1D random network is formed differently from a uniform bilayer film, which also can vary with the modulus of the network. For modulus values lower than the critical point, slippage and rearrangement of NW strands mainly occur and individual strands in the network show an in-plane wavy configuration, which is ideal for structural stretchability. Based on the solvent-assisted prestrain method, letter-sized, large-area stretchable, and transparent electrodes with high transparency and conductivity are achieved, and stretchable and transparent alternating current electroluminescent devices for stretchable display applications are also realized.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201910214.novel optoelectronic devices such as deformable touch screens, [3][4][5][6][7] electronic skins, [8][9][10][11] photovoltaics, [12][13][14] and foldable and stretchable displays. [15][16][17][18][19][20][21] For the successful design of such electronic systems, highly conductive and transparent electrodes are essential, and these electrodes should retain their optoelectrical properties under strain-induced deformation. Among several materials for STEs, [18,[22][23][24][25][26] silver (Ag) nanowire (NW) is the most widely used for flexible transparent electrodes, due to its excellent optical and electrical properties; [27,28] thus, it is also recognized as a promising material in STEs. Although practical optoelectronic applications require large-scale STEs, research on the scalable manufacturing process of STEs is rarely reported. Large-scale Ag NW-based electrodes are manufactured using a variety of scalable manufacturing processes, such as roll-toroll slot-die coating, [29,30] bar casting, [31,32] and spray coating; [33] however, most of the conventional large transparent electrodes (%T ≈ 90%) exhibit flexibility with polymeric substrates and no stretchability. This is because the yield strain of individual Ag NWs is only ≈1.5% in the stretching direction. [34] Structure-assisted stretchability, [35] a process that provides brittle materials with stretchability, can be an ideal approach to accommodate large applied strains without fracturing the materials. Many studies of stretchable electr...

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“…This can also be explained by micro-wrinkles, which have been known for mitigating effective strain applied on stretchable devices. 45,46 In addition, the resistance varied by ~12% after the cycles, making the NHSE among the most robust electrodes in recent state-of-theart works 34,36,43,44,[47][48][49][50] (Figure 2E, Movie S1, Tables S1 and S2). Moreover, the normalized electrical resistance changes merely against twisting, bending, and 25 000-bending cycles, as shown in Figure S8.…”

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