Gate-controlled VO<sub>2</sub> phase transition for high-performance smart windows.

Chen, Shi; Wang, Zhaowu; Ren, Hui; Chen, Yuliang; Yan, Wensheng; Wang, Chengming; Li, Bowen; Jiang, Jun et al. · Sci Adv · 2019

basic_science · Level V

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Abstract

Vanadium dioxide (VO<sub>2</sub>) is a promising material for developing energy-saving "smart windows," owing to its infrared thermochromism induced by metal-insulator transition (MIT). However, its practical application is greatly limited by its relatively high critical temperature (~68°C), low luminous transmittance (<60%), and poor solar energy regulation ability (<15%). Here, we developed a reversible and nonvolatile electric field control of the MIT of a monoclinic VO<sub>2</sub> film. With a solid electrolyte layer assisting gating treatment, we modulated the insertion/extraction of hydrogen into/from the VO<sub>2</sub> lattice at room temperature, causing tristate phase transitions that enable control of light transmittance. The dramatic increase in visible/infrared transmittance due to the phase transition from the metallic (lightly H-doped) to the insulating (heavily H-doped) phase results in an increased solar energy regulation ability up to 26.5%, while maintaining 70.8% visible luminous transmittance. These results break all previous records and exceed the theoretical limit for traditional VO<sub>2</sub> smart windows, making them ready for energy-saving utilization.