Abstract
Designing materials with a negative feedback function is beneficial for achieving temperature regulation inside a greenhouse. VO2 has been studied extensively because of its low insulator-to-metal transition temperature (IMT). In this study, reflection changes during a VO2 phase transition were investigated. Glass fiber cloth was used as a substrate, as it is stable and soft. A VO2 thin film on a glass fiber cloth whose surface contained 96% V4+ and 4% V5+ was prepared using an inorganic sol-gels method. The insulator-to-metal transition temperature was decreased by 38 °C, which was observed from the reflection curve detected using an angle-resolved spectrometer. This decrease in IMT occurred mainly because of the presence of V5+, which causes destabilization of the monoclinic phase of VO2. When the greenhouse temperature was increased from 30 °C to 40 °C, the reflected intensity of VO2 on glass fiber cloth decreased by 22% for the wavelength range of 400 nm to 800 nm. In addition, the angle-independent property of the VO2 thin film was observed using an angle-resolved spectrometer. Owing to its thermo-reflective properties, the thin film can serve as a soft-smart-mirror (SSM) inside a greenhouse to stabilize the temperature, playing a negative feedback role.
Highlights
Plants can grow rapidly in greenhouses because of the proper CO2 concentration, humidity and temperature in this environment
By adjusting the technological parameters of the experiment, the insulator-tometal transition temperature (IMT) of the VO2 thin film was further decreased to 38 °C, which resulted from incorporating a proper proportion of V5+
Glass fiber cloth was used as the substrate of the VO2 thin film
Summary
The angle-independent property of the VO2 thin film on the glass fiber cloth is beneficial for the stability of temperature in a greenhouse because this property can homogenously produce heat from reflected light. The reflection of the VO2 thin film on the glass fiber cloth at a wavelength range of 250 nm to 2500 nm at 20 °C, 30 °C, 35 °C, 45 °C, 60 °C and 75 °C was observed using a Lambda 750 S (PerkinElmer Co., Ltd), shown in the Supporting Information Fig. S3(e). FDTD solution was used to analyze the reflection of the VO2 thin film as the temperature changed for different wavelength values
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