Stretchable and transparent electrodes scale up to large areas
Designed for use in stretchable displays, the new electrodes were demonstrated to operate reliably even under 50% of stretching or when twisted and rolled. The proof of concept consisted of the KIST logo patterned as a transparent ZnS:Cu alternating-current electroluminescent (ACEL) device formed with wavy Ag nanowire-based stretchable electrodes connecting the two sides of the electroluminescent layer, on an elastomeric substrate the size of an A4 paper.
transparent ZnS:Cu alternating-current electroluminescent
(ACEL) device with wavy Ag nanowire-based stretchable and
transparent electrodes.
Here the silver nanowires, only tens of nanometers in diameter, are first spread in a random network of straight nanowires on a pre-stretched sheet of polydimethylsiloxane (PDMS). But instead of releasing the strain and buckling or breaking some of the nanowires in the process, the researchers wetted them with solvents (water). This solvent annealing step, as they describe the process in a paper titled «Buckling Instability Control of 1D Nanowire Networks for a Large‐Area Stretchable and Transparent Electrode» published in the journal of Advanced Functional Materials reduces the frictional resistance between the individual nanowires in the nanowire networks as they become wet.
ZnS:Cu ACEL devices under diverse mechanical deformations,
including 40% stretching.
In particular, each silver nanowire can be worked with in water and rearranged into a curved nanowire structure with a large radius of curvature, so that a structure capable of stably stretching can be realized. Since the nanowires do not experience any unstable conditions, there are no nanowire network fractures or nanowire layer peeling.
By fabricating a silver nanowire network in this way, the research team was able to stretch the substrate and its nanowires by at least 50% of the initial length, stably maintaining transparency and conductivity for approximately 5,000 stretching-relaxing cycles. The team also found that this type of material could be produced using an inexpensive and environmentally-friendly process that uses ethanol and water as solvents.
“The stretchable and transparent electrodes made using wavy silver nanowire networks developed through this research have a high degree of electrical conductivity that is not changed by any deformation”, said Dr. Sang-Soo Lee at KIST
“Since the technology can be used for mass production, it is expected to have a great impact on markets related to wearable electronic devices, such as high-performance smart wear, and the medical equipment field”, added KIST’s Dr. Jeong Gon Son.
Korea Institute of Science and Technology – https://eng.kist.re.kr/kist_eng/main/
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