Bridging to Commercialization: Record‐Breaking of Ultra‐Large and Superior Cyclic Stability Tungsten Oxide Electrochromic Smart Window

Abstract Electrochromic smart windows (ESWs) can significantly reduce energy consumption in buildings, but their cost‐effective, large‐scale production remains a challenge. In this study, the instability of black phosphorus is leveraged to induce the growth of the tungsten oxide film through its decomposition process, inspired by the 2D material‐assisted in situ growth (TAIG) method. This approach results in the preparation of large‐scale, high‐performance WO_3‐x·nH₂O (n < 2) films. Characterization techniques and DFT calculations confirm efficient regulation of structural water and oxygen vacancies during TAIG preparation. The WO_3‐x·nH₂O films exhibit excellent electrochromic (EC) properties, including high transmittance modulation (74.2%@1100 nm), fast switching time (t_c = 5.5 s, t_b = 3.8 s), high coloration efficiency (124.7 cm² C⁻¹), and superior cyclic stability (transmittance modulation retained 94.7% after 20 000 cycles). Ultra‐large WO_3‐x·nH₂O film are prepared via a simple immersion process, and fabricated into a large‐area ESW under facile laboratory conditions, demonstrating the economic and practical feasibility of this approach in industrial‐scale production. Operated by the intelligent control circuit, the ESW exhibits remarkable EC properties and cyclic stability This research represents a milestone in improving the performance and industrial‐scale production of ESWs, bridging the gap to the commercialization of EC technology.