# Effects of Intrinsic Factors on the Stability of Silver Nanowire-Based Flexible Electrodes
## 3 Results and Discussion
### Effects of Graphene Oxide (GO) Modification on the Stability of AgNW Electrodes  
For AgNW electrodes, the firmness of the connection junctions between nanowires has an important influence on the electrical properties and stability of the electrode. Under physical pressure, the connection between silver nanowires mainly relies on van der Waals  
Figure 8: Schematic diagram of the distributions of silver nanowires on electrodes. Top view: **(a)** low surface density; **(b)** medium surface density; and **(c)** high surface density. Side view: **(d)** PET–AgNWs with medium surface density and **(e)** PVA–AgNWs with medium surface density. forces, which are easily affected by external temperature and light. If the connections of silver nanowires can be combined with certain chemical bonds, this is expected to improve the stability of the electrodes. For this reason, graphene oxide (GO) was used to modify the silver nanowire electrodes in the electrode preparation process. Since GO has good hydrophilicity, it can easily cover the silver nanowire cross junctions and parts of the silver nanowires, which enhances the junction connection force through its large \(\Pi\)-bonding and reduces the contact resistance between the silver nanowires and wires. The electrical and optical properties of the PET-AgNW electrodes before and after GO modification are shown in Figure 9. It can be seen that the GO layer improves the electrical properties of the electrodes, and the conductivity of the electrodes is improved more obviously when the surface densities of AgNPs are small. The coverage of GO on the AgNW electrodes also has a certain effect on the light transmittance of the electrodes. The average transmittance in the visible range of PET-AgNWs/GO is 85.02%, which is lower than the one of PET-AgNWs (92.24%). Assuming that the transmittance decreases by about 2.75% for each additional mono-atomic layer of GO, it can be estimated that the coverage thickness of GO is about two-three atomic layers according to the decrease in optical transmittance before and after GO coverage. The thermal stability of GO-modified AgNW electrodes at 80 \({}^{\circ}\)C and the light stability under high optical power density (25.8-27.0 W/m\({}^{2}\)) were investigated and the experimental results are shown in Figure 10. The silver nanowire surface densities were set at 126 mg/m\({}^{2}\). It was found that the thermal and light stabilities of the AgNW electrodes are improved after GO surface modification. After 7 \(\times\) 24 h at 80 \({}^{\circ}\)C, the change rates of the square resistance of the PET-AgNWs and GO-modified PET-AgNW-GO electrodes are 98% and 69.4%, respectively, and the degradation rate of the electrical resistance is reduced by about 29% after GO treatment. After 7 \(\times\) 24 h of high-power illumination, the change rates of the square resistance of PET-AgNWs and PET-AgNW-GO electrodes are 49.3% and 32.7%, respectively, and the degradation rate of the resistance is reduced by about 33% after GO treatment. Figure 9: The electrical and optical properties of the PET–AgNW electrodes before and after GO modification. (**a**) Square resistance and (**b**) optical transmittance. To explore the reason for GO enhancing the stability of the electrodes, electron microscope scans were performed on the PET-AgNW electrodes and PET-AgNW-GO electrodes each after continuous 7 \(\times\) 24 h of heat treatment at 80 \({}^{\circ}\)C, and the SEM results are shown in Figure 11. It was found that there are amounts of nanoparticles on the PET-AgNW surfaces without GO surface treatment (as shown in Figure 11a), while the nanoparticles on the surfaces of the PET-AgNWs with GO are hard to be identified for the encapsulation of GO (as shown in Figure 11b). This indicates that the covering of silver nanowires and the contact intersections with GO can block the oxygen and water in the environment and prohibit the generation of silver nanoparticles.