Recently, a research group led by Prof. LI Guanghai from Hefei Institutes of Physical Science of Chinese Academy of Sciences, used a new method to develop thermochromic film with excellent luminous transmittance and solar modulation ability.
The research results were published in Materials Horizons.
VO2(M) is a common thermochromic material capable of transitioning from a semiconductor to a metal state at a specific temperature (68°C). This transition affects the transparency of near-infrared light, making it useful for applications like energy-saving windows, optoelectronic switches, and temperature sensors. However, current methods for producing VO2(M) face challenges such as high hydrothermal temperature requirements and the formation of large particles.
In this study, researchers developed a method to prepare high-quality VO2(M) nanocrystals using a combination of hydrothermal and heat treatment processes.
Initially, they synthesized ultrafine VOOH nanoparticles under mild hydrothermal conditions. These nanoparticles were then heated to produce high-purity VO2(M) nanocrystals. The team also investigated how different heat treatment times affected the phase transition temperature and optical properties of VO2 particles.
To enhance the environmental durability of VO2, researchers encapsulated the nanocrystals in silica shells (VO2@SiO2). They explored how the thickness of these shells affected the optical properties of the material through theoretical simulations. The resulting VO2@SiO2/PVP thin films displayed impressive thermochromic abilitites. They can efficiently regulate solar heat, achieving a 14.91% increase in energy efficiency while maintain a high level of luminous transmittance at 62.29%.
"Our findings may inspire the development of more straightforward and efficient processes for producing high-performance VO2-based films for various applications," said Dr. WU Liangfei, first author of the paper.
The preparation of VOOH and the optical properties of VO2-based thermochromic film. (Image by WU Liangfei)
