Parameter Space Design of a Guest-Host Liquid Crystal Device for Transmittance Control

Nam, Seung Min; Oh, Seung-Won; Kim, Sang Hyeok; Huh, Jae Won; Lim, Eunjung; Kim, Jin Hong; Yoon, Tae Hoon

doi:10.3390/cryst9020063

Cited by 10 publications

(5 citation statements)

References 32 publications

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“…Our experimentation aimed to determine the optimal dye concentration and cell gap for the GHLC cell by calculating transmittance differences in the xand y-directions while systematically varying these parameters. Leveraging an optimization algorithm [23], we identified the LC-dye combination that yielded a high transmittance difference. Ultimately, our optimal configuration incorporated E7 LC material (with optical birefringence ∆n: 0.2255, dielectric anisotropy ∆ε: 14.1, and transition temperature T NI : 63.3 • C sourced from Merck, Darmstadt, Germany) paired with black dye X12 (provided by BASF, Ludwigshafen, Germany) (as depicted in Figure 3a) [24].…”

Section: Resultsmentioning

confidence: 99%

Energy-Efficient Liquid Crystal Smart Window with a Clear View

An,

Choi,

2023

Crystals

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In this study, we enhance the angular-selective light absorption capabilities of guest–host liquid crystal (GHLC) cells by introducing a novel design featuring a uniform lying helix (ULH) structure. Previously GHLC cells, predominantly vertically aligned cells absorbed obliquely incident light but compromised x-direction visibility. In stark contrast, our ULH-based design allows incident light to seamlessly traverse transmittance in both z- and x-directions while efficiently obstructing oblique incident light in the y-direction. Our innovative ULH-based GHLC cell achieves an impressive optical performance. Specifically, it attains a substantial transmittance rate of 56.7% in the z-direction. Furthermore, in oblique views encompassing both the x- and y-directions, it maintains competitive transmittance rates of 44.2% and 29.5%, respectively. This strategic design not only ensures clear and unobstructed views for building occupants in the z- and x-directions but also contributes significantly to energy conservation by preventing oblique incident light from penetrating, thus reducing cooling requirements. Our ULH-based GHLC cell represents a breakthrough in smart window technology, offering an elegant solution to the challenge of balancing energy efficiency and occupant comfort in architectural settings. This advancement holds promising implications for sustainable building designs by enhancing indoor environmental quality while mitigating energy consumption for cooling, ultimately redefining the potential of smart windows in contemporary architecture.

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Section: Resultsmentioning

confidence: 99%

Energy-Efficient Liquid Crystal Smart Window with a Clear View

An,

Choi,

2023

Crystals

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“…On the other hand, the GHLC cell exhibits weak absorption when the dye molecules are aligned perpendicular to the incident light. The transmittance of a homogeneously aligned LC cell for a parallel and perpendicular polarization direction relative to the dye molecules’ absorption axis can be expressed as , where T 0 is the transmittance of the homogeneously aligned LC cell without a dye molecule and α ∥ and α ⊥ are the dye-doped LCs’ parallel and perpendicular absorption coefficients, respectively. Furthermore, c represents the dye concentration and d is the cell gap.…”

Section: Resultsmentioning

confidence: 99%

Controlling the Pretilt Angles of Guest–Host Liquid Crystals via a Hydrophilic Polyimide Layer through Oxygen Plasma Treatment

Liang

Wang

Zhu

et al. 2022

ACS Appl. Electron. Mater.

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The control of the liquid crystal (LC) alignment is an important factor for practical applications. The conventional method typically used is the rubbing of the polyimide (PI) layer. However, it is difficult to obtain intermediate pretilt angles by employing such a method. In this paper, control of the pretilt angle of the LC is achieved by modifying the surface wettability of the PI films via oxygen plasma treatment. A new mode for guest–host liquid crystal (GHLC) smart windows is achieved with intermediate initial transmittance by controlling the pretilt angle, which can turn from the initial state to either the transparent or dark states. Different modes for the GHLC-based smart windows can be fabricated that are dependent on the environmental conditions.

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“…To achieve a high transmittance difference between normal and oblique incidences, we found the optimum dye concentration and cell gap by following the optimization algorithm reported in [50], because they affect the transmittance of a GHLC cell. Depending on the applications, we could design a GHLC cell with a high contrast ratio by increasing the cell gap and dye concentration.…”

Section: Design Principles Of the Devicementioning

confidence: 99%

Smart Window Based on Angular-Selective Absorption of Solar Radiation with Guest–Host Liquid Crystals

Yoon

2021

Crystals

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In this study, we analyzed angular-selective absorption in a guest–host liquid crystal (GHLC) cell for its application in smart windows. For reducing the energy consumption, angular-selective absorption is desired because the light transmitted through windows during the daytime is predominantly incident obliquely from direct sunlight. Owing to the absorption anisotropy of guest dichroic dyes, a GHLC cell can absorb the obliquely incident light, while allowing people to see through windows in a normal view. Therefore, the cell can provide a comfortable environment for occupants, and reduce the energy required for cooling by blocking the solar heat incident from the oblique direction. The GHLC cell can be switched between the transparent and opaque states for a normal view. The rising (falling) time was 6.1 (80.5) ms when the applied voltage was 10 V.

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Parameter Space Design of a Guest-Host Liquid Crystal Device for Transmittance Control

Cited by 10 publications

References 32 publications

Energy-Efficient Liquid Crystal Smart Window with a Clear View

Energy-Efficient Liquid Crystal Smart Window with a Clear View

Controlling the Pretilt Angles of Guest–Host Liquid Crystals via a Hydrophilic Polyimide Layer through Oxygen Plasma Treatment

Smart Window Based on Angular-Selective Absorption of Solar Radiation with Guest–Host Liquid Crystals

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