Dual-Band Modulation of Visible and Near-Infrared Light Transmittance in an All-Solution-Processed Hybrid Micro–Nano Composite Film

Abstract

Smart windows with controllable visible and near-infrared light transmittance can significantly improve the building's energy efficiency and inhabitant comfort. However, most of the current smart window technology cannot achieve the target of ideal solar control. Herein, we present a novel all-solution-processed hybrid micronano composite smart material that have four optical states to separately modulate the visible and NIR light transmittance through voltage and temperature, respectively. This dual-band optical modulation was achieved by constructing a phase-separated polymer framework, which contains the microsized liquid crystals domains with a negative dielectric constant and tungsten-doped vanadium dioxide (W-VO) nanocrystals (NCs). The film with 2.5 wt % W-VO NCs exhibits transparency at normal condition, and the passage of visible light can be reversibly and actively regulated between 60.8% and 1.3% by external applied voltage. Also, the transmittance of NIR light can be reversibly and passively modulated between 59.4% and 41.2% by temperature. Besides, the film also features easy all-solution processability, fast electro-optical (E-O) response time, high mechanical strength, and long-term stability. The as-prepared film provides new opportunities for next-generation smart window technology, and the proposed strategy is conductive to engineering novel hybrid inorganic-organic functional matters.

Electro-Optical Properties of a Polymer Dispersed and Stabilized Cholesteric Liquid Crystals System Constructed by a Stepwise UV-Initiated Radical/Cationic Polymerization

“…As reported in the literature, in the first step a porous polymer network is obtained by UV irradiation of isotropic acrylate monomers (IAMs). Secondly, an electric field is applied simultaneously with UV-light exposure, the liquid crystal acrylate monomers (LAMs) within the ChLC domains being crosslinked to form homeotropically aligned polymer fibers in the porous matrix [22][23][24][25]. During the first stage some of the LAMs are consumed by radical polymerization under UV light.…”

“…During the first stage some of the LAMs are consumed by radical polymerization under UV light. To leave sufficient LAMs for forming the oriented polymer fibers in the second UV polymerization step, the curing time of UV irradiation in the first stage should be strictly controlled, which is not beneficial for the polymer morphology control or further optimization of the electro-optical properties of the PD&SChLC film [22][23][24][25]. To date, liquid-crystalline vinyl-ether monomers (LVMs) have not been investigated in constructing a PD&SChLC system.…”

Reaction‐Induced Phase Separation: A Strategy to Synthesize Azobenzene‐Modified All‐Optical PDLC Devices

“…The film is opaque due to the difference of refractive indices between the dispersed nematic phase and the isotropic polymeric matrix. PDLC devices aim to couple mechanical stability of polymer with the electro‐optical properties of liquid crystals, forming composites with considerable potential in a range of applications including flexible displays, smart windows, and optical devices …”

“…[1][2][3][4][5][6][7][8][9] The cooperative movement of orientation among the molecules of liquid crystal and azobenzene or interruption of the order of the liquid-crystalline phase caused by the trans-cis chromophore photoisomerization has been reported in literature since composites with considerable potential in a range of applications including flexible displays, smart windows, and optical devices. [21][22][23][24][25][26][27][28][29] A variety of works are found in the literature in which azobenzene moieties are added in PDLC-type device formulations, in most cases in order to improve their properties and performance (e.g., optical transmission, contrast ratio, switching behavior, and absorbance factor). [30][31][32][33][34][35] However, a great effort has been made on this field to obtain photoresponsive or optically controllable composite films, attractive for specific applications in photonics and optoelectronics (e.g., optical sensors, optical shutters, diffractive optical elements, filters, and spatial light modulators).…”

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.…”