Improved performance of co-sputtered Ni-Ti oxide films for all-solid-state electrochromic devices

Thin films of Ni-Ti oxide were co-sputtered by reactive direct current magnetron sputtering and their structures, morphologies, and compositions were investigated by X-ray diffraction, atomic force microscopy and X-ray photo-electron spectroscopy. Their electrochromic (EC) performances were studied using cyclic voltammetry, alternating current impedance and optical transmittance measurements. The proper addition of Ti helps the films achieve excellent EC behavior, including the stable coloration-bleaching cycles, high optical transmittance modulation (∼78%), great coloration efficiency (96 cm² C^-1) and low alternating current impedance. Finally, the multiple-layer stacks ITO/NiO_x:Ti/PVB(Li⁺)/WO₃/ITO were laminated based on the optimization of NiO_x:Ti single layers. A large optical contrast (∼60%), a fast response time (3.2 and 4.4 s) and a good durability were obtained for the all-solid-state full EC device.