Structure‐Dependent Trap Passivation in WO 3 Enables Ultra‐Stable Electrochromic Devices

ABSTRACT Electrochromic materials are the core component of electrochromic devices (ECDs) and are expected to offer transformative potential for practical optoelectronic applications. However, ion trapping caused by the trap effect limits their long‐term stability in practical implementation. Here we elucidate the structure‐dependent trap passivation dynamics using amorphous WO 3 (a‐WO 3 ) and amorphous/crystalline WO 3 (a/c‐WO 3 ) as models. Ab initio molecular dynamics simulations reveal that embedded ions (M) form M‐oxide and M‐tungstate species, coupling with W 4+ to induce ion trapping. But this process is delayed due to the higher formation energy barriers of the species evolving in a/c‐WO 3 compared to those in a‐WO 3 . Multiple characterization results visualize the trap passivation dynamics revealed by the simulations above. Leveraging this, a/c‐WO 3 ‐based ECDs achieve 70.5% optical contrast at 700 nm and ultra‐stability with <0.1% degradation after 10,000 cycles. This framework enables ultra‐stable WO 3 ECDs, advancing durable electrochromics for sustainable technologies.