Roll-to-roll sputtered and patterned Cu(2−x)O/Cu/Cu(2−x)O multilayer grid electrode for flexible smart windows

We fabricated cost-effective Cu(2−x)O/Cu/Cu(2−x)O multilayer grid electrodes using roll-to-roll (RTR) sputtering and patterning processes for use as transparent and flexible electrodes in flexible smart windows. To optimize the patterned Cu(2−x)O/Cu/Cu(2−x)O multilayer grid, the electrical and optical properties of the Cu(2−x)O/Cu/Cu(2−x)O multilayer grid electrodes were investigated as a function of grid width and pitch, which directly influence the filling factor of the grid. At the optimized grid width of 16 and pitch of 600 μm, the Cu(2−x)O/Cu/Cu(2−x)O multilayer grid had a sheet resistance of 7.17 Ohm per square and an optical transmittance of 87.6%. In addition, the mechanical properties of the optimized Cu(2−x)O/Cu/Cu(2−x)O multilayer grid electrode was compared to those of brittle ITO electrodes to demonstrate its outstanding flexibility. To show the potential of the Cu(2−x)O/Cu/Cu(2−x)O multilayer grid for smart windows, we fabricated a flexible and transparent thin film heater (TFH) and a flexible electrochromic (EC) device, which are key components of smart windows. The low saturation voltage of the Cu(2−x)O/Cu/Cu(2−x)O grid-based TFH and the fast on–off performance of the Cu(2−x)O/Cu/Cu(2−x)O grid-based EC device indicates that the RTR-processed Cu(2−x)O/Cu/Cu(2−x)O multilayer grid is promising as a low-cost and large-area flexible transparent electrode for high-performance smart windows.