Mechanochemical Synthesis of Amorphous MoO _3‐x Quantum Dots for All‐In‐One Electrochromic Devices

Abstract Electrochromic metal oxides enable dynamic regulation of color and light transmission, offering significant potential for smart windows and energy‐efficient displays. However, the widespread of electrochromic devices suffers from poor cost‐effectiveness due to the intricate material synthesis processes and complex device structure. Herein, the study presents a mechanochemical method for mass‐producing amorphous MoO _3‐x quantum dots (QDs) with abundant oxygen vacancies. Through combined shear exfoliation and chemical oxidation of MoS ₂ precursors, ligand‐free QDs (4.4 nm average size) are achieved under ambient conditions. Moreover, the innovative all‐in‐one electrochromic device is designed based on the amorphous MoO _3‐x QDs film, which greatly simplifies the device construction and fabrication process. Due to the facilitated ion transport inside the amorphous MoO _3‐x QDs, the resulting device exhibits excellent performance, including a large transmittance modulation (ΔT = 84.2% at 600 nm), high coloration efficiency (97.5 cm ² C ⁻¹ ) and long‐term stability (90.2% after 400 cycles). Furthermore, the study demonstrates an energy‐efficient electrochromic display with low driven voltage (1 V), high contrast, as well as the prolonged optical memory effect up to 7 days. These results not only provide a scalable mechanochemical synthesis route for defect‐engineered metal oxide QDs but also open new opportunities for the development of energy‐saving electrochromic displays.