VO2, as a promising material for smart windows, has attracted much attention, and researchers have been continuously striving to optimize the performance of VO2-based materials. Herein, nitrogen-incorporated VO2 (M1) thin films, using a polyvinylpyrrolidone (PVP)-assisted sol–gel method followed by heat treatment in NH3 atmosphere, were synthesized, which exhibited a good solar modulation efficiency (ΔTsol) of 4.99% and modulation efficiency of 37.6% at 2000 nm (ΔT2000 nm), while their visible integrated transmittance (Tlum) ranged from 52.19% to 56.79% after the phase transition. The crystallization, microstructure, and thickness of the film could be regulated by varying PVP concentrations. XPS results showed that, in addition to the NH3 atmosphere-N doped into VO2 lattice, the pyrrolidone-N introduced N-containing groups with N–N, N–O, or N–H bonds into the vicinity of the surface or void of the film in the form of molecular adsorption or atom (N, O, and H) filling. According to the Tauc plot, the estimated bandgap of N-incorporated VO2 thin films related to metal-to-insulator transition (Eg1) was 0.16–0.26 eV, while that associated with the visible transparency (Eg2) was 1.31–1.45 eV. The calculated Eg1 and Eg2 from the first-principles theory were 0.1–0.5 eV and 1.4–1.6 eV, respectively. The Tauc plot estimation and theoretical calculations suggested that the combined effect of N-doping and N-adsorption with the extra atom (H, N, and O) decreased the critical temperature (τc) due to the reduction in Eg1.
|Original language||English (US)|
|State||Published - Dec 26 2022|
Bibliographical noteKAUST Repository Item: Exported on 2023-01-02
Acknowledgements: This research was funded by the Natural Science Foundation of Hubei Province (grant number 2019CFB400), the Research Project of the Hubei Provincial Department of Education (grant number Q20192902), the Fundamental Research Funds for the Central Universities (grant number xzy012022024), the Research Project of the Huanggang Eco-Building and Renewable Resources Research Center (grant number 202204304), and the Doctoral Foundation of Huanggang Normal University (grant number 2019033). The authors thank the Analytical and Testing Center of WUT for the help with carrying out GIXRD, Raman, and FESEM analyses, as well as the State Key Laboratory of Silicate Materials for Architectures for the help with performing the UV/Vis/NIR test.
ASJC Scopus subject areas
- Materials Science(all)