# Effects of Intrinsic Factors on the Stability of Silver Nanowire-Based Flexible Electrodes
## 2 Materials and Methods  
Quartz glass and PET substrates were ultrasonically cleaned with acetone and isopropanol for 20 min each in sequence and were then thoroughly rinsed in deionized water. Next, the chemically cleaned glass and PET substrates were dried by N\({}_{2}\) gas. The substrates surfaces were then treated with ultraviolet/ozone (UV/O\({}_{3}\)) for 15 min. The UV/O\({}_{3}\) treatment was performed by using a UV/ozone cleaner with the power of 55 W to expose the AgNW electrodes to UV radiation at wavelengths of 185 and 254 nm. The UV/O\({}_{3}\) treatment can further remove residual organic contaminants on the substrate surface and improve surface hydrophilicity. This helped AgNW solutions to spread evenly on the surface in the next step. The uniform distribution of AgNPs on the surface is conducive to achieving low resistance and low surface roughness for AgNW electrodes. To accurately control the surface density of AgNPs, a vacuum filtration method was employed to prepare AgNW films with varying surface densities by using AgNW solutions of different mass-to-volume ratios. AgNPs (purchased from Suzhou Gushi New Materials Co., Ltd., Suzhou, China) were dispersed in isopropyl alcohol. The typical length and diameter of the AgNPs were 25 \(\upmu\)m and 30 nm, respectively. Next, a solution of silver nanowires with concentrations of 0.6 mg/L, 0.8 mg/L, 1.0 mg/L, 1.2 mg/L, and 1.6 mg/L was sequentially configured and vacuum pumped, and the silver nanowires were deposited on the filter membrane. Subsequently, a substrate transfer method was utilized to transfer the AgNPs from the filter membranes to PET or PVA substrates. The preparation flows of PET-AgNW and PVA-AgNW samples are shown in Figures 1a and 1b, respectively. For the preparation of PET-AgNW electrodes, as shown in Figure 1a, after tightly attaching the PET to the filter membrane, the silver nanowires were transferred from the filter membrane to the PET substrates after pressure (about 0.6 MPa) loading for two hours. Next, the filter membrane-silver nanowire-PET composite structure was placed in acetone for 15 min and then rinsed with anhydrous ethanol and ultrapure water to completely remove the filter membrane and finally annealed at 110 \({}^{\circ}\)C for 30 min to completely remove the residual organic solvent to obtain the PET-AgNW electrodes. For the preparation of PVA-AgNW electrodes, as shown in Figure 1b, the AgNW films prepared by vacuum filtration were firstly transferred to the quartz glass, then PVA-1799 (provided by GENERAL-REAGENT) solution with a concentration of 8 wt% was drop-coated on AgNW surfaces and spin-coated at 1000 rpm for 30 s. After the PVA was cured to form a film, it was treated sequentially at 40 \({}^{\circ}\)C and 80 \({}^{\circ}\)C, both for 1 h, to improve the uniformity of film formation. Finally, the quartz glass substrates were directly peeled off to obtain the PVA-AgNW electrodes. Figure 1: Schematic diagram of the preparation process of (**a**) PET–AgNW electrodes and (**b**) PVA–AgNW electrodes. In our experiment, a GO solution with tetrahydrofuran as a solvent (concentration of 0.5 mg/mL and pH of 9) was prepared to modify the surface of the AgNW electrodes by the dip-coating method. AgNW electrodes were dipped in GO solution for 1 min, then rinsed with alcohol, and finally annealed at 110 \({}^{\circ}\)C.  
After the AgNW electrodes were prepared, a self-developed photo- and thermo-integrated test system for silver nanowire electrodes was used to evaluate the thermal and light stability of AgNW electrodes. The test system consists of a vacuum pumping system, a vacuum chamber, a temperature heating and control system, a light illumination system, and an impedance analysis system. The vacuum degree of the vacuum chamber can be up to 0.1 MPa, which avoids interference from the external air atmosphere on the stability of the AgNW electrodes.