Electrochromic properties of vertically aligned Ni-doped WO3 nanostructure films and their application in complementary electrochromic devices

Tungsten trioxide (WO3) is a promising electrochromic material for potential applications in architectural and automotive smart windows. Nanostructured WO3 has attracted particular attention over the past few years due to its potential advantages in electrochromic properties. Herein, Ni-doped WO3 nanostructured films were obtained by a seed-free hydrothermal method directly on transparent conducting substrates. The influences of Ni doping on the nanostructure and electrochromic properties of WO3 films were investigated. Compared to pure WO3 films, Ni doping can increase the crystal defects and induce significant changes in the nanostructure, thus affecting the electrochromic performance of WO3 films. Low concentration Ni-WO3 films exhibited a vertically aligned nanorods morphology, ultrahigh optical modulation (over 85% from 600 to 900 nm), high coloration efficiency (60.5 mc2 C−1 at 600 nm) and excellent cycling stability for about 5500 cycles. Finally, the complementary electrochromic device assembled with 1.5% Ni-WO3 and NiO-based films exhibited vivid color change from transparent to black (x = 0.326, y = 0.369, YL% = 3.29%) with maximum transmittance of about 3.5% in the dark state.

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