Figure 2 Images of the nanowire electrodes. SEM images of tilted
(45°) silver nanowire films on PET after (a) annealing and (b) hot rolling. (c) SEM image of a tilted (85°) hot-rolled electrode, which shows that the nanowires are embedded in the substrate surface. Figure 3 shows the AFM images of an annealed electrode and a hot-rolled electrode, with representative line scans underneath. Table 1 summarizes the RMS surface roughness and maximum peak-to-valley data for the annealed and hot-rolled electrodes. The surface roughness of the hot-rolled electrodes, measured buy FG-4592 over three similar samples, dropped 50% compared to that of the annealed sample to 7 nm, and the maximum peak-to-valley height was reduced to less than 30 nm. These roughness values are the lowest among electrodes which do not use additional materials to fill the spaces between the nanowires, and comparable to those that do. Furthermore, for a given sheet resistance, the hot-rolled electrodes are more transparent than electrodes that use additional materials [12, 21]. The maximum peak-to-valley value of the hot-rolled electrodes is lower than the typical layer thicknesses in organic electronic devices. Figure 3 Topography of the hot-rolled electrodes. AFM images of silver nanowire electrodes selleck kinase inhibitor on PET after (a) annealing and (b) hot-rolling. (c), (d) Line scan data corresponding
to the black dashed lines in (a) and (b), PF-04929113 mouse respectively. Table 1 Roughness data of the nanowire electrodes RMS Forskolin order roughness (nm) Max peak-to-valley (nm) Annealed 14 >90 Rolled at 80°C 7 <30 Because different groups use different nanowire diameters for their electrodes, samples
were also fabricated from 90-nm-diameter silver nanowires for comparison. The RMS roughness of the annealed 90-nm-diameter nanowire electrodes was 40 nm, and was 10 nm in the hot-rolled samples. The maximum peak-to-valley height values were 150 and 50 nm for the annealed and hot-rolled electrodes, respectively. The results of the scotch tape test are tabulated in Table 2. The data indicate that, unlike as-deposited and annealed substrates, the nanowires in the hot-rolled electrode adhere to the substrate very well. The sheet resistance of the hot-rolled electrode was 14.0 and 14.1 Ω/sq before and after applying and removing the tape. This level of nanowire adhesion greatly exceeds other nanowire electrodes that were mechanically pressed [7, 27]. Table 2 Percent change in sheet resistance after the tape test on differently prepared electrodes As-deposited Annealed Rolled at 80°C Sheet resistance change after tape test Open circuit 510% 0.9% While bent around a 5-mm rod, the sheet resistance of hot-rolled electrodes increased by less than 1%. When bent 100 times and then returned flat, the resistance was unchanged. In comparison, the sheet resistance of annealed electrodes increased by 3% when bent, and 2% after 100 bending cycles.