# Stability of Silver-Nanowire-Based Flexible Transparent Electrodes under Mechanical Stress
## 3 Results and Discussion
In addition, the RMS roughness was 4.8 nm and 2.5 nm when NOA63 and NOA71 were used as an embedding polymer, respectively, which is similar to that before the application of tensile stress. The AgNW-embedded electrodes showed superior sheet resistance stability compared to ITO electrodes on a PET film and AgNW-exposed electrodes. This was because a AgNW network was formed inside the embedding polymer, regardless of the application of compressive stress or tensile stress. Figure 6: **(a,b)** SEM and (**c,d**) AFM images of the ITO electrode on a PET film (**a,c**) before and (**b,d**) after applying tensile stress. The RMS roughness values before and after applying tensile stress were 1.9 nm and 13.2 nm, respectively. To examine how the compressive and tensile stresses affect the light transmittance characteristics, the optical transmittance in the region of 300-800 nm was measured for various electrodes. Figure 9 shows the optical transmittance of the ITO electrode on the PET film, the AgNW-exposed electrode, and the AgNW-embedded electrode before and after the application of compressive and tensile stress. The ITO electrode on the PET film showed an average transmittance of 77.1% before stress application in the visible light region (400-700 nm). After applying compressive and tensile stresses, the transmittance remained at approximately 77%, regardless of the type of stress. This is because the stress generated cracks on the ITO electrode; however, they were not sufficiently large to change the optical reflection. The AgNW-exposed electrode showed a slightly higher transmittance than the ITO electrode before stress application. Specifically, the average transmission in the visible light region was 83.9%. However, after stress application, the average transmittance decreased, reaching 72.8% and 80.6% when compressive and tensile stresses were applied, respectively. It is speculated that the relatively large reduction in transmittance after the application of compressive stress results from a gap between the substrate and the silver nanowire, which is caused by upward pushing or roughness change. In contrast, the AgNW-embedded electrodes showed similar transmittance regardless of the type of polymer used for embedding and the type of stress. When NOA63 was used as the embedding polymer, the average transmittance in the visible light region was 86.7%. When compressive stress or compressive stress was applied, the average transmittance remained approximately 86%. When NOA71 was used as the polymer for the embedding process, the average transmittance in the visible region was 86.3% before stress application  
Figure 8: (**a–d**) SEM and (**e,h**) AFM images of the AgNW-embedded electrode in (**a,b,e,f**) NOA63 and (**c,d,g,h**) NOA71 (**a,c,e,g**) before and (**b,d,f,h**) after applying tensile stress. The RMS roughness values of AgNW-embedded electrode in NOA63 were 3.7 nm and 4.8 nm before and after applying tensile stress, respectively. The RMS roughness values of AgNW-embedded electrode in NOA71 were 1.6 nm and 2.5 nm before and after applying tensile stress, respectively. Figure 7: (**a,b**) SEM and (**c,d**) AFM images of the AgNW-exposed electrode on a PET film (**a,c**) before and (**b,d**) after applying tensile stress. The RMS roughness values before and after applying tensile stress were 9.8 nm and 9.4 nm, respectively. and remained 86% even when compressive or tensile stress was applied, indicating that the stress had little effect on the transmittance. This is because stress had little effect on the surface morphology and light reflection, as seen in the SEM and AFM images.