Modeling of dual frequency liquid crystal materials and devices

Brimicombe, P. D.; Parry-Jones, Lesley A.; Elston, Steve J.; Raynes, E. P.

doi:10.1063/1.2135410

Cited by 14 publications

(3 citation statements)

References 13 publications

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“…Hence, the Freedericksz mechanism can be exploited to reorient the LC molecules from the equilibrium planar (|| to the substrate) to the field‐driven homeotropic (⊥ to the substrate) configuration with E of f < f c and the return to equilibrium with E of f >> f c . This dual frequency protocol (DFP) is the basis for a variety of devices including switches, retarders, modulators, and displays . The point to be noted is that the dual frequency character exists for the CsLC composite also, although with a slightly higher f c value, and diminished ε a .…”

Section: Resultsmentioning

confidence: 99%

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Satapathy

Santra

Haque

et al. 2019

Advanced Optical Materials

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An assembly of quantum dots (QDs) is an ideal system in which coupling between individual dots through their charge, spin, or optical excitation can be studied. [2] Apart from these fundamental aspects of physics, such systematic studies will have important implications in a wide range of fields from photovoltaic to displays and quantum information processing. [3][4][5][6] Specifically, the organic/inorganic hybrid perovskites [7] such as MAPbX 3 (MA = CH 3 NH 3 ; X = Cl, Br, I) QDs, have several attractive features such as high photoluminescence (PL) quantum yield, high diffusion length, low processing temperatures, low cost and scalable fabrication. Obviously, they have received significant attention owing to their excellent photovoltaic device performance. [8] They are also potential candidates for use in white LEDs, as wide-color-gamut backlight for LCDs, information storage, etc. [9,10] QDs of fully inorganic halide perovskite (IHP) materials such as CsPbX 3 (X = Cl, Br, I) are becoming popular due to their relatively better stability, significant photovoltaic performances, and high PL efficiency (≈90%) with concomitant narrow emission line width . [2] In the quest for high-purity green light from LEDs, the all-inorganic cesium lead halide perovskite QDs have shown promise owing to pure green emission with a narrow bandwidth and high quantum efficiency. Recalling that the efficiency of the LEDs is lower in the green/yellow spectral range, [11,12] the system investigated here may be attractive. Nanosoft composites comprising LCs as host and nanostructures as the guest is an emerging area of research that gets benefitted by the unique characters of the latter in the self-assembling features of LCs. A variety of nanoparticles have been employed to alter/tune the LC properties. In fact, QDs have received their fair share of attention in this regard. [40][41][42][43][44][45][46][47][48] Presence of QDs has been found to diminish the threshold voltage, [49] accelerate the electrooptic response, [49] photorefractivity, [50][51][52][53] increase the birefringence, [54,55] and control PL. [52,53,56] While the organic-inorganic QDs have been extensively studied in photovoltaics, it is the inorganic variety that is gaining importance in recent times. [51][52][53][57][58][59] It may be highlighted that in the previous cases of LC-QD composites, the QDs are spherical, while in contrast, IHPs form cuboids. Thus their incorporation into the LC medium can be expected to generate a tendency for self-assembled shape Fast electrically switchable anisotropic photoluminescence from a nano-soft composite comprising a nematic liquid crystal (LC) and quantum cuboids of a cesium lead halide perovskite is reported. The magnitude of the anisotropy in emission appears to be dictated by the anisotropy of the LC and the capability of the cuboids to form a linear chain, the latter being evidenced through optical and electron microscopy. Application of an ac electric field of small amplitude and its consequent coupling to the LC director ...

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Section: Resultsmentioning

confidence: 99%

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Satapathy

Santra

Haque

et al. 2019

Advanced Optical Materials

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“…Another type of LC materials that suits for fast tuning is dual-frequency liquid crystal (DFLC) [7], which exhibits a positive dielectric anisotropy (Δε ε ∥ − ε ⊥ > 0) when frequency f of applied field is below f c (crossover frequency) while turns to a negative one (Δε < 0) at f >f c . This property enables the possibility of tuning LC orientations by dual-frequency addressing at a relatively low voltage, permitting a fast switching time down to submilliseconds [8,9]. Dual-frequency liquid crystal devices such as optical retarder [10] and variable optical attenuator [11] have been reported with response time ∼0.5 ms at V rms 25 V and ∼0.9 ms at V rms 20 V, respectively.…”

mentioning

confidence: 99%

Fast response dual-frequency liquid crystal switch with photo-patterned alignments

Lin

et al. 2012

Opt. Lett.

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A dual-frequency liquid crystal based optical switch with orthogonally photo-patterned alignments is designed and fabricated. The cell gap is theoretically optimized for high switching performance. The measured extinction ratio of first diffraction order is over 20 dB with a low electric field of 3 V/μm. The switch On-Off time are measured to be 350 μs and 600 μs, respectively, both of which have reached submillisecond scale. Moreover, the switch is polarization independent, which has been predicted theoretically and further proved experimentally. This design is suitable in wide applications requiring fast response and polarizer free properties.

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“…Moreover, we can increase the switching speed of this proposed pi cell by a dual frequency driving method. 10,14,15 The difference of the intensity operational range results from the various profiles of LC director after polymerizations. In the case of the pi cell stabilized in the RB state, the LC director throughout the device is stabilized in a more relaxed ͑i.e., lower tilt͒ state, which thus has higher freedom of switching compared to the pi cell stabilized using the conventional polymerization.…”

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confidence: 99%

High-brightness relaxed-bend state in a pi cell stabilized by synchronized polymerization

Yang

Elston

Raynes

et al. 2008

Applied Physics Letters

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The authors report a synchronized polymer-stabilization technique which can be used to stabilize the nonpermanent states in liquid crystal devices. In this paper, a relaxed-bend state in a pi cell which has a lifetime of only 80ms is observed and then stabilized by this proposed technique. After stabilizing, the pi cell is immune to undesirable recovery into the splay or twist states, and its optical contrast is much higher than that of the conventional polymer-stabilized pi cell.

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Modeling of dual frequency liquid crystal materials and devices

Cited by 14 publications

References 13 publications

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Fast response dual-frequency liquid crystal switch with photo-patterned alignments

High-brightness relaxed-bend state in a pi cell stabilized by synchronized polymerization

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Modeling of dual frequency liquid crystal materials and devices

Cited by 14 publications

References 13 publications

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr3 Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr3 Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Fast response dual-frequency liquid crystal switch with photo-patterned alignments

High-brightness relaxed-bend state in a pi cell stabilized by synchronized polymerization

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Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr₃ Perovskite Quantum Cuboids in a Nematic Liquid Crystal