Enhanced Photoelectrochromic Performance of WO 3 Through MoS 2 and GO–MoS 2 Quantum Dot Doping for Self-Powered Smart Window Application

Photoelectrochromic devices, which combine light-induced color change with energy-efficient optical modulation, have attracted significant attention for applications such as smart windows, displays, and optical sensors. However, achieving high optical modulation, fast switching speeds, and long-term stability remains a major challenge. In this study, we explore the structural and photoelectrochromic enhancements in tungsten oxide (WO 3 ) films achieved by doping with molybdenum disulfide quantum dots (MoS 2 QDs) and grapheneoxide–molybdenum disulfide quantum dots (GO–MoS 2 QDs) for advanced photoelectrochromic devices. X-ray diffraction (XRD) analysis revealed that doping with MoS 2 QDs and GO–MoS 2 QDs leads to a reduction in the crystallite size of WO 3 , as evidenced by the broadening and decrease in peak intensity. Transmission Electron Microscopy (TEM) confirmed the presence of characteristic lattice fringes with interplanar spacings of 0.36 nm, 0.43 nm, and 0.34 nm, corresponding to the planes of WO 3 , MoS 2 , and graphene. Energy-Dispersive X-ray Spectroscopy (EDS) mapping indicated a uniform distribution of tungsten, oxygen, molybdenum, and sulfur, suggesting homogeneous doping throughout the WO 3 matrix. Scanning Electron Microscopy (SEM) analysis showed a significant decrease in film thickness from 724.3 nm for pure WO 3 to 578.8 nm for MoS 2 QD-doped WO 3 and 588.7 nm for GO–MoS 2 QD-doped WO 3 , attributed to enhanced packing density and structural reorganization. These structural modifications are expected to enhance photoelectrochromic performance by improving charge transport and mechanical stability. Photoelectrochromic performance analysis showed a significant improvement in optical modulation upon incorporating MoS 2 QDs and GO–MoS 2 QDs into the WO 3 matrix, achieving a coloration depth of 56.69% and 70.28% at 630 nm, respectively, within 10 min of 1.5 AM sun illumination, with more than 90% recovery of the initial transmittance within 7 h in dark conditions. Additionally, device stability was improved by the incorporation of GO–MoS 2 QDs into the WO 3 layer. The findings demonstrate that incorporating MoS 2 QDs and GO–MoS 2 QDs effectively modifies the structural properties of WO 3 , making it a promising material for high-performance photoelectrochromic applications.