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Precipitating CsPbBr <sub/>3</sub> quantum dots in boro-germanate glass with a dense structure and inert environment toward highly stable and efficient narrow-band green emitters for wide-color-gamut liquid crystal displays
摘要： All-inorganic perovskite CsPbBr3 quantum dots (QDs) are becoming the most popular narrow-band green emitter for use as a critical material in next generation wide-color-gamut backlight displays. However, their intrinsic poor stability greatly hinders their development for practical applications. Herein, CsPbBr3 QDs were successfully precipitated in boro-germanate glass (CsPbBr3 QDs@glass) with well-designed compositions, not only retaining a high photoluminescence quantum yield (PLQY of 43% upon 450 nm excitation) and narrow bandwidth (FWHM of 22 nm), but also showing significantly enhanced stability in relation to water, heat, and UV/blue irradiation. The relative PL intensity of CsPbBr3 QDs@glass was maintained at 60% or 85% after being immersed in water for 22 days or exposed to UV light for 100 hours, respectively. Moreover, CsPbBr3 QDs@glass samples present impressive recovery abilities in thermal cycling experiments or upon intermittent blue light irradiation. Finally, an all-inorganic white light-emitting diode (white LED) achieving 125% of National Television Standards Committee (NTSC) performance was fabricated through employing green-emitting CsPbBr3 QDs@glass and red-emitting Cs2SiF6:Mn4+ phosphor-in-glass (PiG) plates as color convertors. The design rules established here could initiate the further exploration of other glass systems with moderate halide solubilities and low melting temperatures to precipitate highly e?cient and stable CsPbX3 (X = Cl, Br, I) QDs.
关键词： stability,boro-germanate glass,CsPbBr3 quantum dots,wide-color-gamut liquid crystal displays,narrow-band green emitters
更新于2025-09-12 10:27:22
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Dielectric and electro-optic properties of two biphenylyl benzoate-based ferroelectric mesogens with tilted hexagonal phases
摘要： Two partially fluorinated ferroelectric liquid crystals (2F3R, 3F3R) with biphenylyl benzoate core have been investigated by frequency domain dielectric spectroscopy and electro-optic method. Both the compounds exhibit SmC* phase over a wide range of temperature along with tilted hexatic phase SmF* and soft crystal phases SmJ* (in 2F3R) and SmG* (in 3F3R) and one coexistence phase of (SmF*+SmC*). Both BOO phason and tilt phason relaxations are observed in SmF* phase and cooperative relaxation behaviour is also observed in crystal-like smectic phases. Goldstone mode relaxation is observed in SmC* phase and Maxwell Wagner mode is observed in all the phases. In 2F3R soft mode is detected in both SmC* and SmA* phases but not in 3F3R which melts directly to isotropic phase from SmC* phase. Compounds possess moderate values of spontaneous polarisation and exhibit quite sharp electrical response especially in 2F3R. Rotational viscosities, pitch and elastic constant are also measured. Effect of chain length and fluorination on various physical parameters has been discussed.
关键词： soft mode,tilted hexagonal phase,BOO and tilt phason mode,spontaneous polarisation,Ferroelectric liquid crystal,response time
更新于2025-09-12 10:27:22
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Influence of structural parameters on organic semiconducting polymer lasers with an external holographic grating as feedback layer
摘要： We report on the fabrication and characterization of an organic distributed feedback laser excited from a semiconducting polymer gain layer, poly(2-methoxy-5-(20-ethyl-hexyloxy)-p-phenyl-envinylene) (MEH-PPV). A holographic polymer dispersed liquid crystal grating is fabricated on top of the homogeneous MEH-PPV layer as an external cavity. We established a model to calculate the con?nement factor Γ. With the change of laser structural parameters (the refractive index of the grating layer, the ?lm thickness of the MEH-PPV layer, etc.), the con?nement factor Γ changes accordingly. It was found that a single longitudinal lasing mode could be observed only when the con?nement factor Γ was in a speci?c range. Choosing a reasonable thickness of gain ?lm and prepolymer with higher refractive index can obtain a lower threshold emission laser.
关键词： organic distributed feedback laser,lasing mode,semiconducting polymer,holographic polymer dispersed liquid crystal grating,con?nement factor
更新于2025-09-12 10:27:22
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Dielectric and electro-optical properties of zinc ferrite nanoparticles dispersed nematic liquid crystal 4’-Heptyl-4-biphenylcarbonnitrile
摘要： In this work, comprehensive results on dielectric and electro-optical properties of pristine and zinc ferrite (ZnFe2O4) nanoparticles (NPs) dispersed in host nematic 4?-Heptyl-4-biphenylcarbonnitrile (7CB) systems are reported. The dielectric and EO properties of pristine and NPs dispersed (concentrations 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5 wt%) into the host nematic system have been studied. We have seen uniform NPs dispersion into nematic 7CB up to 0.15 wt% concentration of NPs by the POM. The NPs aggregation starts at 0.2 wt% dispersion. It is shown that the dielectric and electro-optical properties are strongly in?uenced by the concentration of NPs in host nematic and applied electric ?eld. The dielectric anisotropy is maximum for the NPs dispersed system of 0.15 wt% concentration. The Birefringence, parallel and perpendicular components of permittivity and conductivity are found to be dependent on temperature and concentration of NPs into host matrix. In pure nematic material, small memory is seen but in NPs dispersed systems noticeable memory is found. In particular, pronounced memory is found for the dispersed system of 0.3 wt% concentration of NPs.
关键词： Nematic liquid crystal,zinc ferrite nanoparticles,birefringence,splay elastic constant,dielectric anisotropy
更新于2025-09-12 10:27:22
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Liquid crystal tunable claddings for polymer integrated optical waveguides
摘要： Optical waveguides in photonic integrated circuits are traditionally passive elements merely carrying optical signals from one point to another. These elements could contribute to the integrated circuit functionality if they were modulated either by variations of the core optical properties, or by using tunable claddings. In this work, the use of liquid crystals as electro-optically active claddings for driving integrated waveguides has been explored. Tunable waveguides have been modeled and fabricated using polymers. Optical functions such as variable coupling and optical switching have been demonstrated.
关键词： tunable cladding,photonic integrated circuit,liquid crystal,polymer waveguide,organic waveguide
更新于2025-09-12 10:27:22
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An efficient and thermally stable dye-sensitized solar cell based on a lamellar nanostructured thiolate/disulfide liquid crystal electrolyte and carbon/PEDOT composite nanoparticle electrode
摘要： A thiolate/disulfide redox based lamellar nanostructured smectic liquid crystal electrolyte with an optimized configuration and a carbon/PEDOT composite nanoparticle electrode were prepared for efficient dye-sensitized solar cells (DSSCs). The configuration of the optimized electrolyte consisted of 1-dodecyl-3-methyl-1H-imidazol-3-ium 1-methyl-1H-tetrazole-5thiolate/di-5-(1-methyltetrazole) disulfide/TBP/LiClO4 in the molecular ratio of 2 : 1 : 1 : 0.1. The carbon/PEDOT composite electrode was developed by electrochemical deposition of PEDOT on a carbon nanoparticle electrode. The additives in the lamellar nanostructured electrolyte were revealed to lower the viscosity of the electrolyte for promoted ion diffusion, as well as benefit the charge transfer process in the DSSC. The carbon/PEDOT nanoparticle electrode was suggested to provide improved catalytic activity and large surface area to favor the charge transfer at the cathode/electrolyte interface of the DSSC. As a result, the DSSC fabricated using the optimized smectic electrolyte, the composite nanoparticle electrode, together with a Z907 sensitized photoanode, attained a maximum power conversion efficiency of 6.5% at 40 °C and stable efficiencies higher than 6.0% within a temperature range from 35 to 55 °C. These results show potential of the optimized smectic thiolate/disulfide electrolyte based DSSCs operating efficiently and stably under outdoor conditions.
关键词： thiolate/disulfide,carbon/PEDOT composite,thermal stability,dye-sensitized solar cells,liquid crystal electrolyte
更新于2025-09-12 10:27:22
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Investigation of dielectric and electro-optical parameters of high birefringent nematic liquid crystal doped with TiO <sub/>2</sub> nanoparticles and its applicability toward liquid crystal displays
摘要： In the present study, anatase TiO2 nanoparticles (NPs) have been doped in three different concentrations into nematic liquid crystal (NLC) 2020 (fluorinated 4’-alkylphenyl-4-isothiocyanatotolanes). The ratio has decreased and increased, response time and contrast respectively for the NLC-NPs composite system. Polarizing optical microscope images reveal that alignment has been improved after the doping of TiO2 NPs. Dielectric measurement study shows that the tan d has been decreased and relaxation frequency shifted toward the lower frequency region for the doped system. The outcome of the present investigation may be very useful in the improvement of electro-optical features of liquid crystal displays.
关键词： Nematic liquid crystal,response time,Contrast ratio,TiO2 nanoparticles
更新于2025-09-12 10:27:22
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Liquid Crystal Based Dielectric Waveguide Phase Shifters for Phased Arrays at W-Band
摘要： In this work, the feasibility of microwave liquid crystal based dielectric waveguide phased shifters is investigated in a phased rod antenna array for the ?rst time. For this, a 1 × 4 rod antenna array is designed including the phase shifters as well as a cascaded E-plane power divider network. As core elements, the phase shifter are designed as continuously tunable subwavelength ?bers, partially ?lled with a newly speci?cally synthesized microwave liquid crystal, exhibiting a maximum FoM 145?/dB at 102.5 GHz. As proof-of-concept, a simpli?ed electric biasing network is developed, demonstrating its beam steering capability by changing the scanning angle between 0?, ?25? and +15? with three different voltage distributions. The antenna array is well matched throughout the complete W-band with a input re?ection below ?10 dB. The measured antenna gain is between 11.5 to 9.1 dBi at 85 GHz accompanied with a side lobe level between ?12 to ?7 dB, depending on the steering con?guration.
关键词： dielectric waveguide,millimeter wave devices,Phased array,microwave liquid crystal
更新于2025-09-11 14:15:04
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - InP-based devices integrating liquid crystals microcells for a tunable laser emission or a wavelength selective photodetection
摘要： Photonic devices with wavelength tuning capabilities are investigated with the use of liquid crystal microcells monolithically integrated onto the surfaces of photodiodes or VCSEL fabricated on InP based materials. For these two devices, we demonstrated that the detected or emitted wavelength can be selected on a tuning range of more than 70 nm in the case of the photodiode, and of more than 20 nm in the case of VCSEL.
关键词： VCSEL,Photodiodes,Liquid-crystal,Optical communications
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Hyperspectral Imaging of Bio-Inspired Tilted Cholesteric Liquid Crystal Structures
摘要： The cholesteric liquid crystal (CLC) phase exhibits a helical structure with a twist axis perpendicular to the local molecular director. When light propagates in the Bragg regime through a CLC slab with a planar texture, the medium gives rise to Bragg reflection, selective in wavelength and in polarization. The characteristics of the Bragg band are tunable by acting on the following structural parameters: the pitch, the helicity sense and the helix orientation. Tuning the latter parameter produces polygonal textures (Fig. 1, center). Such a texture is made of an array of micrometer-scale polygonal cells, acting a network of microlenses with wavelength-tunable focusing properties [1]. Polygonal textures can be found in biological CLCs (for instance, multiwavelength micromirrors the cuticle of scarab beetle Chrysina gloriosa [2]). Here, we perform jointly spectral and spatial characterization of CLCs with oblique helicity through a liquid-crystal-based hyperspectral imaging (HSI), which is a compact and non-destructive technique ideally adapted to characterize mesoscopic samples, both in transmission and reflection [3]. Although liquid crystal have already been used to perform multispectral and hyperspectral imaging, they have not been, to date, the subject of an HSI study. The instrument output is an image with 512*128 pixels, each of them being spectrally resolved. Spectro-spatial properties of the polygonal texture are then measured with unprecedented spectral resolution for tilted CLCs, that is 6 nm over 400-1000nm, while conventional multispectral imaging is limited to a spectral resolution of a few tens of nanometers. Our experimental results are summarized in Fig. 1. In transmission, the mesoscopic chromatic pattern of the studied sample is recovered, and its wavelength-tunable light shaping properties are emphasized with the reconstruction of the hyperspectral datacube of a quarter of polygon. Furthermore, the reflected light analysis of a single polygon (lateral dimension below 15μm) reveals the local tilting of the CLC helical axis, that is the bulk distortion constituting the texture. The signature resides in the fine tuning of the spectral characteristics of the bandgap into the part of a polygon in which the orientation of the helix axis is spatially changing. A correlation between spatial changes and spectral changes on a mesoscopic scale is therefore made possible [4]. These results demonstrate the interest of hyperspectral imaging for the precise study of complex cholesteric components, also existing in biological samples. It thus opens many perspectives to enrich and deepen our knowledge on the fine structure of these materials. Additionally, it is found that polygonal textures may offer practical solutions in numerous applications, from secure authentication to information-enriched imaging, and, particularly, in the field of cryptography.
关键词： wavelength-tunable,Bragg reflection,polygonal textures,cholesteric liquid crystal,hyperspectral imaging
更新于2025-09-11 14:15:04