Multi-stable cholesteric liquid crystal windows with four optical states

Mo, Liyi; Sun, Haitao; Liang, Aihui; Jiang, Xiaofang; Shui, Lingling; Zhou, Guofu; Haan, Laurens T. de; Hu, Xiaowen

doi:10.1080/02678292.2021.1962422

Cited by 13 publications

(12 citation statements)

References 43 publications

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“…Therefore, smart windows are required to achieve intelligent indoor light and thermal management by modulating the visible and infrared light range of sunlight . Up to now, plenty of research about smart windows has been developed, which can adjust transmittance through electro-, − thermal, − photo-, − and mechanoresponses. , Changing the transmittance of smart windows artificially and actively by electrical stimulation requires an external circuit, additional energy consumption, and safety hazards . Photochromic and thermochromic windows are considered cost-effective, stimuli-rational, and energy-efficient for their simple structure, passive light modulation, and zero-energy input characteristics …”

Section: Introductionmentioning

confidence: 99%

Photothermal Dual Passively Driven Liquid Crystal Smart Window

Meng

Gao

et al. 2022

ACS Appl. Mater. Interfaces

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Photochromic or thermochromic liquid crystal (LC) smart windows have attracted wide attention due to their spontaneous transmittance modulation under different environments. There remains a challenge for the LC smart windows that can be modulated with light and temperature simultaneously owing to the difficulty in selecting photothermal molecules. Herein, we selected a photothermal molecule, isobutyl-substituted diimmonium borate (IDI), which shows excellent characteristics of a photothermal material used in smart windows, such as transparency in the visible light range with a slight brown color, good compatibility with the LC system, and excellent photothermal effect compared with common photothermal materials. Thus, a photothermal dual-driven smart window is developed by doping IDI into chiral LC mixtures, which can efficiently modulate the transmittance at different temperatures (or light intensities) by varying the phase state from the homeotropically oriented smectic phase (transparent) to the focal conic cholesteric phase (opaque). The transmittance is high (70%) when the ambient temperature is low and the light intensity is weak, allowing more sunlight to enter the room. The transmittance is low (20%) when the ambient temperature is high and the light intensity is strong, which prevents sunlight from entering the room. The proposed smart window will have a promising application in terms of energy saving and personalized privacy protection.

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Section: Introductionmentioning

confidence: 99%

Photothermal Dual Passively Driven Liquid Crystal Smart Window

Meng

Gao

et al. 2022

ACS Appl. Mater. Interfaces

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“…For example, under the voltage of 3.34 V/µm, the transmittance dropped to less than 15% in the visible region (from 400 to 760 nm). Moreover, the reflection band disappeared under high voltage, which was due to the randomly distributed helical axis of the focal conic state [ 13 ]. It could be noticed that the operational voltage was high, which is attributed to two reasons.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, technologies based on light scattering using LC/polymer composites, such as polymer stabilized LCs (PSLC) and polymer dispersed LCs (PDLC), have been developed to control visible light [ 8 , 9 , 10 , 11 , 12 ]. Smart windows have been developed using smectic/cholesteric liquid crystal (CLC) phases, where the window can be reversibly switched between transparent (planar and homeotropic) and scattering (focal conic) states [ 13 , 14 ]. For technologies controlling IR light, polymer stabilized CLC (PSCLC) has been widely studied [ 15 , 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

Dual-Function Smart Windows Using Polymer Stabilized Cholesteric Liquid Crystal Driven with Interdigitated Electrodes

Jin

Hao

et al. 2023

Polymers

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In this study, we present an electrically switchable window that can dynamically transmit both visible light and infrared (IR) light. The window is based on polymer stabilized cholesteric liquid crystals (PSCLCs), which are placed between a top plate electrode substrate and a bottom interdigitated electrode substrate. By applying a vertical alternating current electric field between the top and bottom substrates, the transmittance of the entire visible light can be adjusted. The cholesteric liquid crystals (CLC) texture will switch to a scattering focal conic state. The corresponding transmittance decreases from 90% to less than 15% in the whole visible region. The reflection bandwidth in the IR region can be tuned by applying an in-plane interdigital direct current (DC) electric field. The non-uniform distribution of the in-plane electric field will lead to helix pitch distortion of the CLC, resulting in a broadband reflection. The IR reflection bandwidth can be dynamically adjusted from 158 to 478 nm. The electric field strength can be varied to regulate both the transmittance in the visible range and the IR reflection bandwidth. After removing the electric field, both features can be restored to their initial states. This appealing feature of the window enables on-demand indoor light and heat management, making it a promising addition to the current smart windows available. This technology has considerable potential for practical applications in green buildings and automobiles.

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“…When an electric field is applied to the bilayer hyper-reflective sample, the small-molecule LC layer is likely to undergo changes from the initial planar aligned state to the focal conic state, and then to the cholesteric fingerprint state, while the polymer layer is less likely to be influenced thanks to the cross-linked structure (Figure S12). , As a result, the sample first becomes pale and hazy, then nearly transparent under L-CPL, due to the changes happening in the LC layer. In contrast, the changes under R-CPL and unpolarized light are much less obvious.…”

Section: Resultsmentioning

confidence: 99%

Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

Wei

Yang

et al. 2022

ACS Appl. Mater. Interfaces

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Cholesteric liquid crystals (CLCs) are chiral photonic materials with selective reflection in terms of wavelength and polarization. Helix engineering is often required in order to produce desired properties for CLC materials to be employed for beam steering, light diffraction, scattering, and adaptive or broadband reflection. Here, we demonstrate a novel photopolymerization-enforced stratification (PES)-based strategy to realize helix engineering in a chiral CLC system with initially one handedness of molecular rotation throughout the layer. PES plays a crucial role in driving the chiral dopant bundle consisting of two chiral dopants of opposite handedness to spontaneously phase separate and create a CLC bilayer structure that reflects left-and right-handed circularly polarized light (CPL). The initially hidden chiral information therefore becomes explicit, and hyper-reflectivity, i.e., reflecting both left-and right-handed CPL, successfully emerges from the designed CLC mixture. The PES mechanism can be applied to structure a wide range of liquid crystal (LC) and polymer materials. Moreover, the engineering strategy enables facile programming of the center wavelength of hyper-reflection, patterning, and incorporating stimuli-responsiveness in the optical device. Hence, the engineered hyper-reflective CLCs offer great promise for future applications, such as digital displays, lasing, optical storage, and smart windows.

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Multi-stable cholesteric liquid crystal windows with four optical states

Cited by 13 publications

References 43 publications

Photothermal Dual Passively Driven Liquid Crystal Smart Window

Photothermal Dual Passively Driven Liquid Crystal Smart Window

Dual-Function Smart Windows Using Polymer Stabilized Cholesteric Liquid Crystal Driven with Interdigitated Electrodes

Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

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