Li4Ti5O12: A Visible‐to‐Infrared Broadband Electrochromic Material for Optical and Thermal Management

Mandal, Jyotirmoy; Du, Sicen; Dontigny, Martin; Zaghib, Karim; Yu, Nanfang; Yang, Yuan

doi:10.1002/adfm.201802180

Cited by 154 publications

(78 citation statements)

References 46 publications

(31 reference statements)

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“…Electrochromic materials employ reversible redox reaction that affects material's electronic transitions, and, as a consequence, the absorption profile of the solar spectra [28]. Several metal oxides have been reported for applications in smart windows among which the tungsten oxide (WO3) being the most popular one due to material's fast switching time between opaque and clear sates, as well as high visible light transmission in the clear state [40,41]. Thermochromic smart windows employ materials that exhibit phase transition between the semiconducting monoclinic phase (clear state) and the metallic rutile phase (opaque state) as a function of temperature.…”

Section: Introductionmentioning

confidence: 99%

Improving thermo-optic properties of smart windows via coupling to radiative coolers

et al. 2020

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In this work we first solve the radiative heat transfer problem in one dimension to perform a comparative analysis of the time averaged performance of the partially transparent radiative windows and radiative coolers. In doing so we clearly distinguish the design goals for the partially transparent windows and radiative coolers and provide optimal choice for the material parameters to realize these goals. Thus, radiative coolers are normally non-transparent in the visible, and the main goal is to design a cooler with the temperature of its dark side as low as possible relative to that of the atmosphere. For the radiative windows, however, their surfaces are necessarily partially transparent in the visible. In the cooling mode the main question is rather about the maximal visible light transmission through the window at which the temperature on the window somber side does not exceed that of the atmosphere. We then demonstrate that transmission of the visible light through smart windows can be significantly increased (by as much as a factor of 2) without additional heating of the windows via coupling of the windows to the radiative coolers using transparent cooling liquid that flows inside of the window and radiative cooler structures. We demonstrate that efficient heat exchange between radiative coolers and smart windows can be realized using small coolant velocities (sub 1mm/s for ~1m-large windows) or even using a purely passive gravitationally driven coolant flows between a hot smart window and a cold radiative cooler mounted on top of the window with only a minimal temperature differential (sub-1K) between the two. We believe that our simple models complimented with an in-depth comparative analysis of the standalone and coupled smart windows and radiative coolers can be of interest to a broad scientific community pursuing research in these disciplines.

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Section: Introductionmentioning

confidence: 99%

Improving thermo-optic properties of smart windows via coupling to radiative coolers

et al. 2020

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“…A black body that absorbs broadband omnidirectional radiation is an ideal absorber, which has applications in energy harvesting, photodetectors, photothermal energy generation, and concealment . Film‐based absorbers, such as multiple pairs of stacked metal/dielectric films or multilayer‐stacked films, are suitable for the large‐area fabrication.…”

Section: Performance and Fabrication Characteristics Of The State‐of‐mentioning

confidence: 99%

Large‐Area, Ultrathin Metasurface Exhibiting Strong Unpolarized Ultrabroadband Absorption

Yan

Jiang

et al. 2019

Advanced Optical Materials

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despite their sophisticated designs, most of these devices only work in a narrow bandwidth range and require complicated fabrication procedures. These issues impede large-area applications for energy harvesting and photothermal energy generation. A large-area, wide angular tolerance, broadband absorber with ultrathin metallic nanoparticles has been recently proposed. [38] However, the suitability of this device for photothermal energy generation applications remains unclear because the stability of these metallic nanostructures at high temperatures is usually low.Due to the outstanding properties, such as compatibility with the complementary metal oxide semiconductor (CMOS) processes, high temperature resistance, large loss in the visible range, and high reflectivity in the infrared (IR) range, [39] titanium nitride (TiN) has emerged as an ideal material for the preparation of near-perfect absorbers for the high-temperature solar/thermophotovoltaics applications. [39,40] A 5-cycle TiN/silicon dioxide (SiO 2 ) multilayer-based absorber has been reported with an average solar absorptivity of 0.68 [1] and a near-perfect absorption, which requires further enhancement. The high average absorptivity of ≈95% by a ringlike TiN layer using a metamaterial absorber was achieved for the entire visible range. [41] However, the bandwidth of these devices is limited in the visible range. For ultrabroadband light absorption, 3D-truncated TiN nanopillars have been demonstrated for the visible and NIR spectral regions with an average absorptivity of 0.94. [42] This TiN nanopillar-based device, which comprises silicon nanopillars with a large thickness (>1 µm), typically requires expensive, time-consuming fabrication processes, and its thermal emissivity is not verified. Therefore, there are few experimental reports on the large-area ultrathin TiN-based metasurfaces for the strong ultrabroadband light absorption with low thermal emissivity.In this paper, we demonstrate wide-angle ultrabroadband strong light absorption that covers almost the whole solar spectrum (250-2250 nm) by the TiN-based metasurface with an ultrathin thickness (330 nm) on a quartz substrate. The metasurface incorporates dielectric cylinder arrays, a TiN layer, and SiN x layers. This metasurface fundamentally differs from the previously reported absorbers. This device, which uses a symmetrical SiO 2 grating, is independent of incident polarization. Specifically, the carefully designed metasurface exhibits a prominent absorption of both polarizations over wide angles. The outstanding performances of this absorber are realized by Large-area, ultrathin devices with strong ultrabroadband absorption and high angular tolerance are in demand for applications such as ultraviolet protection, energy harvesting, photodetectors, and thermal imaging technology. Although there have been considerable efforts to design and fabricate these devices, the simultaneous realization of all desired properties has not been achieved. A 330 nm thick metasurface with an area of 3 cm 2 is e...

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“…Electrochromic materials employ reversible redox reaction that affects material's electronic transitions, and, as a consequence, the absorption profile of the solar spectra [34]. Several metal oxides have been reported for applications in smart windows among which the tungsten oxide (WO3) being the most popular one due to material's fast switching time between opaque and clear sates, as well as high visible light transmission in the clear state [46,47]. Thermochromic smart windows employ materials that exhibit phase transition between the semiconducting monoclinic phase (clear state) and the metallic rutile phase (opaque state) as a function of temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Thermochromic smart windows employ materials that exhibit phase transition between the semiconducting monoclinic phase (clear state) and the metallic rutile phase (opaque state) as a function of temperature. Vanadium dioxide (VO2) based materials are the most popular ones to regulate transmission of the visible and near-IR light using the thermochromic effect [47]. At the same time, even in the clear state transmittance of the visible light through this material is relatively low because of the material strong absorption and high reflection [46].…”

Section: Introductionmentioning

confidence: 99%

Simple models for the operation of partially transparent radiative windows and their comparison to the radiative coolers

Skorobogatiy¹,

Caloz²,

Zhung³

2019

Preprint

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In this work we solve approximately the radiative heat transfer problem in one dimension to perform a comparative analysis of the time averaged performance of the partially transparent radiative windows and radiative coolers. Our physical model includes the atmosphere, the window, and the backwall that are all in the thermal equilibrium with each other, and that can exchange energy via radiative heat transfer or convection. Moreover, we use a simplified two-state model for the optical properties of an atmosphere and a window material which assumes two distinct sets of the optical reflection/absorption/transmission parameters in the visible/near-IR versus mid-IR spectral ranges. Furthermore, we have distinguished the design goals for the partially transparent windows and radiative coolers and provided optimal choice for the material parameters to realize these goals. Thus, radiative coolers are normally non-transparent in the visible, and the main goal is to design a cooler with the temperature of its dark side as low as possible compared to that of the atmosphere. For the radiative windows, however, their surfaces are necessarily partially transparent in the visible. In the cooling mode, therefore, the main question is about the maximal visible light transmission through the window at which the temperature on the window somber side does not exceed that of the atmosphere. We believe that our simple physical models complimented with an in-depth comparative analysis of the radiative windows and coolers can be of interest to a number of scientists and engineers pursuing research in these disciplines.

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Li₄Ti₅O₁₂: A Visible‐to‐Infrared Broadband Electrochromic Material for Optical and Thermal Management

Cited by 154 publications

References 46 publications

Improving thermo-optic properties of smart windows via coupling to radiative coolers

Improving thermo-optic properties of smart windows via coupling to radiative coolers

Large‐Area, Ultrathin Metasurface Exhibiting Strong Unpolarized Ultrabroadband Absorption

Simple models for the operation of partially transparent radiative windows and their comparison to the radiative coolers

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