Sputtering Flexible VO₂ Films for Effective Thermal Modulation

Abstract

Flexible vanadium dioxide (VO 2 ) thermochromic films show great potential for large-scale fabrication and possess broader applications compared with VO 2 coatings on rigid substrates. However, the fabrication of flexible VO 2 films remains a challenge so far, leading to the scarcity of research on flexible VO 2 films for smart windows. With the aim to obtain a flexible VO 2based films with excellent optical properties and a long service life, we designed and successfully fabricated a flexible ITO/VO 2 /ITO (IVI) film on the colorless transparent polyimide substrate, which could be directly attached to glasses for indoor temperature modulation. This flexible IVI film effectively enhances the luminous transmittance (T lum ) and solar modulation ability (ΔT sol ) (15 and 68% increase relative to a VO 2 single layer), reduces the thermal emissivity (ε T ) (50.7% decrease relative to a VO 2 single layer), and exhibits better durability than previously reported structures. Such excellent comprehensive performance offers it great potential in practical applications on smart windows. This work is supposed to provide a new strategy for facile direct fabrication of flexible VO 2 films and broaden the applications of flexible VO 2 in more coatings and devices.

Thermochromic Energy Efficient Windows: Fundamentals, Recent Advances, and Perspectives

“…(f) Δ T sol , T lum , and durability of previous reported flexible VO 2 -based films. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

A solar/radiative cooling dual-regulation smart window based on shape-morphing kirigami structures

“…Despite the promise of these dual-control smart window designs, they still face limitations in terms of durability and modulation capability. For example, the thermal-responsive vanadium dioxide (VO 2 ) is prone to oxidation 21,22 and although existing remedies such as sealing 23,24 and encapsulation 25 can improve the durability of VO 2 , this is at the cost of defunctionalizing VO 2 's e Broadband modulation ability. Stimuliresponsive hydrogels and reversible metal electrodeposition also suffer from durability issues due to factors such as vulnerability to drying 26,27 and electrochemical cell performance degradation.…”

Gradient Variation Oxygen-Content Vanadium–Oxygen Composite Films with Enhanced Crystallinity and Excellent Durability for Smart Windows

“…Controlling the heat and light exchange between windows and the outside world is one of the key ways to reduce energy consumption in buildings. , VO 2 , with a phase transition temperature of 68 °C, is the closest known phase transition material to room temperature . Through the metal–insulator transition (MIT) process, VO 2 demonstrates reversible changes in optical, electrical, and other properties. , Vanadium dioxide (VO 2 )-based smart windows are widely recognized as an effective solution for building energy-saving due to their intelligent temperature response and zero-energy consumption. , VO 2 can effectively regulate the building temperature because it can control the heat escaping or injected into the enclosed space by adjusting the transmittance and reflectance of different wavelengths of the solar radiation spectrum. − …”