Crystalline/amorphous tungsten oxide core/shell hierarchical structures and their synergistic effect for optical modulation

High-performance electrochromic films with large color contrast and fast switching speed are of great importance for developing advanced smart windows. In this work, crystalline/amorphous WO3 core/shell (c-WO3@a-WO3) nanowire arrays rationally are synthesized by combining hydrothermal and electrodeposition methods. The 1D c-WO3@a-WO3 core/shell hierarchical structures show a synergistic effect for the enhancement of optical modulation, especially in the infrared (IR) region. By optimizing the electrodeposition time of 400 s, the core/shell array exhibits a significant optical modulation (70.3% at 750 nm, 42.0% at 2000 nm and 51.4% at 10 mu m), fast switching speed (3.5 s and 4.8 s), high coloration efficiency (43.2 cm(2) C-1 at 750 nm) and excellent cycling performance (68.5% after 3000 cycles). The crystalline/amorphous nanostructured film can provide an alternative way for developing high-performance electrochromic materials. (C) 2015 Elsevier Inc. All rights reserved.