posted on 2021-07-27, 11:37authored byNan Shen, Shi Chen, Run Shi, Shuzhang Niu, Abbas Amini, Chun Cheng
The critical challenge for the practical
applications of VO2-based smart windows is to nucleate
and propagate the phase
transformation in the ambient condition while maintaining a balance
between solar energy regulation and visible light transmittance. Doping
proves effective in the modification of the thermochromic performance
in VO2 but always causes unfavorable degradation accompanied
with the significant reduction of phase transition temperature. Joule
heating has been introduced in VO2-based devices to activate
the metal–insulator transition (MIT) at ambient temperature.
A synergy between these two strategies is necessary to achieve a well-balanced
performance of VO2 films at the appropriate temperature.
Here, we systematically investigate the thermochromic properties of
tungsten (W)-doped VO2 composite films with Joule heating
triggered MIT. The phase transition temperature of VO2 is
effectively decreased by 21.6 °C per at. % W, and the balanced
luminous transmittance (Tlum = 50.8%)
and solar energy modulation ability (ΔTsol = 11.4%) are achieved at 0.6 at. % W doping. Importantly,
as a synergetic result of W doping and hysteresis behavior of MIT
in VO2, the optimal infrared blocking performance can be
retained at a reduced cost of energy consumption and at the ambient
temperature down to 47 °C. This is comparable to the glass window
temperature in the summer in subtropical and tropical regions. This
result suggests quite low and even zero energy consumption to maintain
the optimal infrared blocking performance of VO2 films.
This study provides a practical and advanced setup for operable and
efficient smart windows in ambient conditions.