The effects of surface plasmon resonance coupling effect on the solar energy modulation under high transmittance of VO2 nanostructure

Improving solar energy modulation ability while maintaining high visible-light transmittance has been a challenge of VO2 application in smart window. The improvement of solar modulation ability will often be accompanied by the decrease of visible light transmittance. In the present work, we propose a solution to improve the solar energy modulation ability and maintain high visible-light transmittance through etching the sputtered VO2 thin film by dilute sulfuric acid, which is based on the strong resonance coupling effect. We prepared planar VO2 thin film and acid-treated film with the similar transmittance. Their transmittances (Tlum) are about 57%. However, the solar energy modulation rate (ΔTsol) of acid-treated VO2 particles is increased by 277.8% compared with planar VO2 film. FDTD method is used to calculate the optical properties of acid-treated and planar VO2 film, the simulation results are consistent with experimental results. The increment of ΔTsol is related to the surface plasmon resonance and its coupled electromagnetic field of metallic state VO2. These results demonstrate that surface plasmon resonance and its coupling effect can be used to further enhance the solar energy modulation while maintaining the visible light transmittance. We hope these results will contribute to the area of smart window and other fields.