Transmission electron microscopy (TEM) samples were prepared by mechanically rubbing the electrodes onto copper grids overlayed with ultra-thin amorphous carbon. Both PF 2341066 bright-field images and energy dispersive spectroscopy (EDS) spectra were obtained in the TEM. For comparison purposes, additional
nanowire electrodes were prepared, but no current was passed across them. Rather, one electrode was left in air and its sheet resistance was monitored over the period of 1 year. Other electrodes were annealed in an atmospheric furnace each at various temperatures and times. These electrodes were imaged in the SEM at various stages to see how the electrode morphology evolved throughout the annealing process. Results and discussion Electrode failure measurements An SEM image of a prepared nanowire electrode is shown in Figure 1a.
The transparency of all electrodes was nearly constant across all visible wavelengths, as similarly found by other groups [3, 10, 11]. The electrodes prepared for the stability experiments had sheet resistances ranging from 12 Ω/sq (with a corresponding transparency of 91% at a wavelength of 550 nm) to 37 Ω/sq (with a transparency of 94% at 550 nm). Figure 1b shows the evolution of the voltage and surface temperature of a 12 Ω/sq nanowire VRT752271 electrode as 17 mA/cm2 of current was passed across it. As was typical with all samples measured, the voltage (and therefore resistance) gradually increased with time, Immune system and then suddenly jumped to 30 V once the electrode failed. The power dissipated in the electrode is P = IV,
so with a constant current and a gradually increasing voltage, the surface temperature gradually increased over time as well until electrode failure. Figure 1 Silver nanowire electrode and its long-term characteristics. (a) SEM image of an as-prepared electrode. (b) Voltage and surface temperature of a 12 Ω/sq sample when a constant current density of 17 mA/cm2 was applied across the electrode. Figure 2a shows that under a constant current density, electrodes with a higher sheet resistance fail more quickly. Higher sheet resistance electrodes have sparser nanowire networks, and thus the current density in the individual nanowires is higher than in lower resistance electrodes. Joule heating is also higher in more resistive films, since P = IV = I 2 R. The surface temperatures immediately preceding the electrode failure of the four samples measured for Figure 2a, from the lowest to highest sheet resistance, were 55°C, 70°C, 100°C, and 102°C, respectively. Figure 2 Dependency of failure time on resistance and current density. (a) The number of days to failure versus sheet resistance, when conducting 17 mA/cm2 across samples with different resistances. (b) The relationship between the number of days to failure and current density, as measured with three different 30 Ω/sq electrodes.