Electrochromic electrode with high optical contrast and long cyclic life using nest-like porous doped-Sm WO3 films

Electrochromic materials (ECMs) have received attention owing to its huge potential applications, such as smart dimming windows, static displays, and electrochromic capacitors. High optical contrast and long cyclic life of ECMs are extremely critical for practical applications. In this work, the WO 3 and rare earth Sm-doped WO 3 (WSm x , x  = 2.0, 3.0, 4.0, 5.0) films were constructed by hydrothermal system, and then their morphology and electrochromic performance were explored. The morphology of the WO 3 film was transformed from an urchin-like to a nest-like porous structure by adding 4.0%Sm into the hydrothermal system. In comparison with the WO 3 film, the WSm4.0 film displayed higher optical contrast and cyclic life, which was resulting from its crystalline and amorphous mix phases, and nest-like porous structure with high Li  +   diffusion coefficient and strong structure stability. The optical contrasts of the WO 3 and WSm4.0 films were 57.9% and 61.4% at 633 nm wavelength, respectively. Furthermore, WSm4.0 film exhibited optical contrast of around 70% range from 700 to 1100 nm wavelength. Remarkably, WSm4.0 film still retained 91.7% and 73.6% of primitive optical contrast after 6000 and 10000 cycles, respectively. The nest-like porous WSm4.0 film are promising for assembling electrochromic smart windows with long cyclic life and high optical contrast.