# Effects of Intrinsic Factors on the Stability of Silver Nanowire-Based Flexible Electrodes
## 3 Results and Discussion  
### Effects of Flexible Substrates on the Stability of AgNW Electrodes  
Figure 2 shows the relative variations in square resistance of the PET-AgNW and PVA-AgNW electrodes with time under different temperatures treatments, which characterizes the thermal stability of these two kinds of electrodes. The AgNW surface densities for both PET-AgNW and PVA-AgNW electrodes are 95 mg/m\({}^{2}\). It can be seen that both the PET-AgNW and PVA-AgNW electrodes are stable at a room temperature of 25 \({}^{\circ}\)C, as the square resistance of both electrodes remains unchanged with time. However, when the ambient temperature is 65 \({}^{\circ}\)C, the resistances of the two kinds of electrodes change significantly with time, and their trends of change are consistent. The resistance of the electrodes first decreases slightly with time, showing that the conductivity of the electrodes improves slightly within 24 h, and then the resistance starts to increase rapidly with time. The reason for the initial decrease may be that the small amounts of water, acetone, isopropanol, and anhydrous ethanol left on the electrodes would evaporate at high temperatures, which increases the conductivity of the electrodes. With the increased time at high temperatures, the oxygen and moisture present in the environmental air would react with the silver nanowires and generate non-conductive oxides and sulfides on the surfaces of the nanowires, which decreases the electrical conductivity of the AgNW electrodes [10]. After 7 \(\times\) 24 consecutive hours at 65 \({}^{\circ}\)C, the change in square resistance of the PET-AgNW electrodes is close to 70%, which is more than twice the change in square resistance of the PVA-AgNW electrodes of 32.3%. When the ambient temperature increases to 80 \({}^{\circ}\)C, the changes in the resistance rate become greater. In our experiments, it was found that the AgNW electrodes behaved in a stable way when the ambient temperature was not higher than 40 \({}^{\circ}\)C. However, we have not made further experiments to clarify whether there is a critical temperature to trigger the degradation of AgNW electrodes significantly. It is noted that in Figure 2 the increase rates in the resistances of both PET-AgNW and PVA-AgNW  
electrodes with time are not constant when the ambient temperature is 65 \({}^{\circ}\)C or 80 \({}^{\circ}\)C. Considering the standard deviation of the relative change in resistance in our experimental system is 0.2%, and the change in resistance increase rates is more than 1%, we think the change in resistance increase rates does not originate from the measurement errors, but is the result of the changes in surface state of AgNPs with time. Figure 3 shows the relative variations in square resistance of the PET-AgNW and PVA-AgNW electrodes with time, respectively, under low and high optical power density irradiation at an ambient temperature of 25 \({}^{\circ}\)C, which characterizes the light stability of the two kinds of electrodes. The AgNW surface densities for both PET-AgNWs and PVA-AgNWs electrodes are 95 mg/m\({}^{2}\). It can be seen from Figure 3 that the square resistance of both electrodes increases continuously with time, both under low and high optical power density irradiation. The change rate in the square resistance of the PET-AgNW electrodes is significantly larger than that of the PVA-AgNW electrodes under the same light intensity and illumination time, which shows that PVA-AgNW electrodes are more stable than PET-AgNW electrodes. It is also noted that in Figure 3 the increase rates in the resistances of both PET-AgNW and PVA-AgNW electrodes with time are not constant under low or high light illuminations. Compared to PET-AgNW electrodes, PVA-AgNW electrodes show much less change at high temperatures. The main reason for the difference in stability is that the silver nanowires are bound to the substrate in different ways.