Synergistic regulation of key process parameters influencing the structure and electrochromic performance of sol–gel derived WO3 films: amorphous superiority at 100 °C

Abstract

To address the practical application challenges of slow response speed and inadequate stability in WO₃ electrochromic films, this study fabricated such films using the sol–gel method and systematically investigated the effects of key process parameters, including the aging time of peroxotungstic acid (PTA) sol, spin-coating speed, and annealing temperature, on the films’ microstructure, crystal structure, and electrochromic performance. The findings demonstrated that 15 h was the optimal aging time for the PTA sol, effectively optimizing the film formation quality. The ideal spin-coating speed was 2000 rpm, enabling precise regulation of the film thickness and performance. Notably, the amorphous WO₃ films annealed at 100 °C exhibited outstanding comprehensive electrochromic properties, attributed to their unique three-dimensional disordered polygonal ionic channel structure. Specifically, these films achieved an optical modulation amplitude of 64.4%, a bleaching response time of 1.2 s, a coloring response time of 3.1 s, a coloration efficiency of 42.5 cm² C⁻¹, and favorable cycling stability. In contrast, crystalline WO₃ films formed via high-temperature annealing suffer from ion-trapping effects, leading to incomplete bleaching. This work offers effective strategies and a theoretical foundation for the design and preparation of high-performance WO₃-based electrochromic films from the dual perspectives of process regulation and structural mechanisms.