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. 2017 Jan 27:7:41336.
doi: 10.1038/srep41336.

Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin Al2O3: Thermal, Ambient, and Mechanical Stabilities

Byungil Hwang  1 , Youngseo An  2 , Hyangsook Lee  2   3 , Eunha Lee  3 , Stefan Becker  1 , Yong-Hoon Kim  2   4 , Hyoungsub Kim  2
Affiliations

Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin Al2O3: Thermal, Ambient, and Mechanical Stabilities

Byungil Hwang et al. Sci Rep. .

Abstract

There is an increasing demand in the flexible electronics industry for highly robust flexible/transparent conductors that can withstand high temperatures and corrosive environments. In this work, outstanding thermal and ambient stability is demonstrated for a highly transparent Ag nanowire electrode with a low electrical resistivity, by encapsulating it with an ultra-thin Al2O3 film (around 5.3 nm) via low-temperature (100 °C) atomic layer deposition. The Al2O3-encapsulated Ag nanowire (Al2O3/Ag) electrodes are stable even after annealing at 380 °C for 100 min and maintain their electrical and optical properties. The Al2O3 encapsulation layer also effectively blocks the permeation of H2O molecules and thereby enhances the ambient stability to greater than 1,080 h in an atmosphere with a relative humidity of 85% at 85 °C. Results from the cyclic bending test of up to 500,000 cycles (under an effective strain of 2.5%) confirm that the Al2O3/Ag nanowire electrode has a superior mechanical reliability to that of the conventional indium tin oxide film electrode. Moreover, the Al2O3 encapsulation significantly improves the mechanical durability of the Ag nanowire electrode, as confirmed by performing wiping tests using isopropyl alcohol.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1
Changes in (a) optical transmittance/haze and (b) sheet resistance of the Ag and Al2O3/Ag nanowire electrodes as a function of the annealing temperature. The annealing time is 20 min.
Figure 2
Figure 2
Changes in (a) optical transmittance/haze and (b) sheet resistance of the Al2O3/Ag nanowire electrode after annealing at 380 °C as a function of the annealing time.
Figure 3
Figure 3
Plan-view SEM images of (a–c) bare Ag and (d–f) Al2O3/Ag nanowire electrodes after annealing at different temperatures. Inset of (d) is a tilted SEM image showing the conformal coating of an ultra-thin ALD-Al2O3 layer on a single Ag nanowire.
Figure 4
Figure 4. Sheet resistances of the Ag and Al2O3/Ag nanowire electrodes before and after exposure to ambient conditions with a relative humidity of 85% at 85 °C for 1,080 h.
Figure 5
Figure 5
(a) Fractional resistance changes of the Ag and Al2O3/Ag nanowire electrodes under 2.5% applied strain as a function of the number of bending cycles: up to (a) 1,200 and (b) 500,000 cycles. The corresponding value for the reference ITO sample is also included in (a).
Figure 6
Figure 6
Optical microscopy images of (a,b) Ag and (c,d) Al2O3/Ag nanowire electrodes: (a,c) and (b,d) are before and after the wiping test (five times) using IPA, respectively. Here, Ts, Hz, and Rs in each panel represent measured transmittance, haze, and sheet resistance, respectively. Insets are the photographs of LED lights connected to the each specimen.
See this image and copyright information in PMC

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