Coating strategies for improving electrochromic WO3 quantum-dots

WO3 quantum-dot electrochromic devices have exhibited significant commercial potential, owing to their ultra-fast response speed, wide optical transmittance modulation, and low-cost preparation process. However, the application of quantum-dots in electrochromic devices has encountered bottleneck issues. Specifically, quantum-dots tend to agglomerate or be eroded by electrolyte. Herein we propose strategies to manipulate the coating material of quantum-dots at the molecular scale for these issues, achieving single-dot and multi-dot coating of quantum-dots. The single-dot coated quantum-dot device has a transmittance modulation of 54.5% and 69.1% at wavelengths of 580 and 800 nm, respectively, with colouring efficiencies of 101.7 and 163.1 cm2/C, and a bleaching/colouring time of 4.0/7.5 s. Meanwhile, the transmittance modulation of the multi-dot coated quantum-dot device is up to 77.4% at 580 nm and 86.0% at 800 nm with colouring efficiencies of 80.7 and 135.3 cm2/C and a bleaching/colouring time of 11.0/13.0 s. After 10,000 CV-tests, the multi-dot coated quantum-dot device still operates stably. These indicate advantages of the strategies. Quantum-dot electrochromic devices face challenges such as agglomeration and electrolyte erosion, hindering their commercial potential. Here, the authors address these issues by developing molecular-scale coating strategies, achieving enhanced transmittance modulation and stability, with significant implications for advancing high-performance, cost-effective electrochromic technologies.