Gate-controlled VO ₂ phase transition for high-performance smart windows

Abstract

Vanadium dioxide (VO2) 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 VO2 film. With a solid electrolyte layer assisting gating treatment, we modulated the insertion/extraction of hydrogen into/from the VO2 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 VO2 smart windows, making them ready for energy-saving utilization.

Unraveling the Mott-Peierls intrigue in vanadium dioxide

“…Vanadium dioxide (VO 2 ) is a transition metal compound with tremendous potential for technological applications, essentially in reason of its nearly room temperature metal-to-insulator transition [1][2][3][4][5][6][7][8][9][10]. Over the years, VO 2 has been subject to an intense investigation, which dates back to the first decades of the last century [11][12][13][14][15][16][17][18][19][20], but that is yet alive [21][22][23] and, to some extent, debated [24][25][26][27][28][29][30]. At the critical temperature T c ∼ 340 K and ambient pressure, VO 2 undergoes a first-order transition from a metal (T > T c ) to an insulator (T < T c ) [31,32], both phases being paramagnetic [33][34][35].…”

3D Printed Smart Windows for Adaptive Solar Modulations

“…[ 12–14 ] Nevertheless, due to its intrinsic physical properties, the application of VO 2 on energy‐saving smart window still faces one major challenge which is to reduce τ c while maintaining both high luminous transmission ( T lum ) and the solar modulation ability (Δ T sol ) simultaneously. [ 15 ] Various approaches have been applied to address this issue including but not limited to doping, [ 16–20 ] antireflection coating, [ 21–23 ] biomimetic structuring, [ 24–26 ] compositing, [ 27–31 ] photonic structuring, [ 32,33 ] kirigami‐inspired structuring. [ 34 ] However, the usual trade‐off relationship between these three major index τ c , Δ T sol , and T lum is often observed, especially for doping techniques.…”

“…[ 34 ] However, the usual trade‐off relationship between these three major index τ c , Δ T sol , and T lum is often observed, especially for doping techniques. [ 16–20 ]…”

Advances in Inorganic All-solid-state Electrochromic Materials and Devices

“…当今社会, 能源短缺和环境污染的形势日益严 峻, 节能环保屡次被搬上国家和政府的工作议题, 驱动了该领域材料研发的热度 [1] 。作为节能环保领 域的代表性材料, 场致变色材料是一类能在外场 (电场、温度、光照、气氛)刺激下发生可逆光学变 化的物质统称, 主要分为电致变色 [2][3] 、 热致变色 [4][5] 、 光致变色 [6][7] 和气致变色 [8][9] 材料等, 如图 1 所示。 其 中, 电致变色材料能主动响应外加电场而产生稳 定、 可逆的光学变化, 应用在建筑及汽车窗玻璃, 可 起到灵敏调控内部温度及光强的作用, 兼具节能及 舒适度的特点 [10] 。 1 电致变色材料 电致变色材料在光热调控智能窗 [11] 领域相较 于二氧化钒基热致变色材料具有独特优势, 通过微 弱的电信号即可灵敏地反馈出显著可逆的颜色变化, 这种主动可控的调节模式更易于满足实际应用所需, 并且在显示器 [15] 、储能器件 [16] 以及军用红外隐身等 领域也得到了广泛应用。近年来, 国内外众多课题 组均致力于电致变色的基础研究与应用拓展。中国 科学技术大学俞书宏团队 [17] 通过朗格缪尔-布吉特 (L-B)技术开发的基于 Ag/W 18 O 49 纳米线共组装体的 柔性电致变色器件, 可实现不同图案的显示效果, 如图 2 所示, 并且此结构易于大面积制备, 颜色深 浅通过 W 18 O 49 纳米线的层数动态可调, 并具备一定 的柔性和机械稳定性, 有望在显示面板领域得到应 用。而王金敏等 [18] 则利用普鲁士蓝的电化学特性, 作为电致变色层实现了自供能电致变色-自充电透 明电池的双功能器件, 从图 3 可以看出, 器件褪色 对应放电过程, 而显色对应充电过程。这一设计利 用了电致变色器件内部的电化学反应实现了自身的 充放电, 在不引入外部电源的前提下进行有效调光, 且在放电过程中能驱动外接二极管发光。 图 1 场致变色材料体系示例 Fig. 1 Schematic diagram of chromogenic system (a) Al 3+ based electrochromic device and its light modulation [11] ; (b) Gate-controlled VO 2 phase transition by tuning hydrogenating level for high-performance smart windows [12] ; (c) Illustration of reversible photochromic reaction in PC-PCN (photochromic porous coordination network) [13] ; (d) Schematic description of the adsorption and diffusion of a H atom along WO x based gasochromic thin film [14] 图 2 Ag/W 18 O 49 纳米线共组装体柔性电致变色器件示意图(a)和照片(b~e) [17] Fig. 2 Schematic diagram (a) and photographs (b-e) of flexible electrochromic device of Ag/W 18 O 49 nanowire co-assemble [17] 图 3 双功能器件作用机理示意图 [18] Fig.…”