Improvement In Optical Transmission Research Articles

Exploring the electro-optical properties of nematic liquid crystal through incorporation of ZnCuGaS2 core/shell quantum dots

ABSTRACT The current study focuses on elucidating the interaction mechanisms between ZnCuGaS2 quantum dots (QDs) and nematic liquid crystals (NLCs) (5CB), intending to comprehend how this interaction leads to the alteration of electro-optical properties of the host material. Various concentrations of QDs were incorporated into NLCs and investigated to examine their emission and transmittance characteristics. Remarkably, an enhancement (~68%) in photoluminescence was observed for the concentration of 0.04 wt. %, adding an intriguing aspect to the findings. A notable decrease in the threshold voltage, from 1.5 V (in pure NLC) to 0.5 V, was observed for the optimised concentration (0.04 wt. %) calculated using transmittance-voltage measurement. This sample exhibited a noteworthy improvement in optical transmission, showing an increase by 2.7 times compared to pure NLC. Fundamentally, the introduction of QDs leads to a reduction in light leakage centres and ionic impurities, consequently enhancing radiative recombination. Moreover, the memory effect of the sample was evident in the capacitance-voltage data, revealing that the NLC with QDs significantly increased the capacitance value from 290 pF to 466 pF when compared to the pure NLC. The objective of the present research is to examine the impact of QDs on NLC concerning key parameters such as mentioned above.

Effect of Electron and Proton Irradiation on Structural and Electronic Properties of Carbon Nanowalls.

In this work, a complex experimental study of the effect of electron and proton ionizing radiation on the properties of carbon nanowalls (CNWs) is carried out using various state-of-the-art materials characterization techniques. CNW layers on quartz substrates were exposed to 5 MeV electron and 1.8 MeV proton irradiation with accumulated fluences of 7 × 1013 e/cm2 and 1012 p/cm2, respectively. It is found that depending on the type of irradiation (electron or proton), the morphology and structural properties of CNWs change; in particular, the wall density decreases, and the sp2 hybridization component increases. The morphological and structural changes in turn lead to changes in the electronic, optical, and electrical characteristics of the material, in particular, change in the work function, improvement in optical transmission, an increase in the surface resistance, and a decrease in the specific conductivity of the CNW films. Lastly, this study highlights the potential of CNWs as nanostructured functional materials for novel high-performance radiation-resistant electronic and optoelectronic devices.

INFLUENCE OF DOPANTS AND DEPOSITION TEMPERATURE ON THE OPTICAL AND SOLID STATE PROPERTIES OF DYE-SENSITIZED NOVEL NANOHYBRID ZnxSnyOz THIN FILMS DEPOSITED USING SPRAY PYROLYSIS

Dye-sensitized Novel Nanohybrid ZnxSnyOz thin films were prepared on glass substrates using spray pyrolysis technique. The dye used is extract from the leaves of tectona grandis. A 0.1M of Zn2+ and 1% was used respectively. Depositions were done at different substrate temperature of 50oC, 100oC, and 150oC. The effect Zn2+ ion and dye extract from tectona grandis leaves on optical and solid state properties of the films were examined and analysed. The result showed that the absorbance of the undoped SnO thin films at various substrate temperatures vary from about 0.1-0.7. The absorbance generally increased with deposition/ substrate temperature exhibiting a maximum for films deposited at 150oC. The average transmittance of both un-doped and Zn2+ doped SnO thin films at 350nm is above 90% regardless of the film thickness. The dye doped samples showed an improvement in optical transmission at 625nm. The reflectance spectra of all films exhibited a similar trend. Peak reflectance was observed at 350nm for un-doped and Zn2+ doped samples of SnO thin films while peak reflectance can be observed at 625nm for dye doped samples. It is also observed that the band gaps of the dye doped samples are lower: 1.55eV- 1.83eV than those of the Zn2+ doped samples: 1.60eV – 2.20eV. This showed that the incorporation of the dye shifted the fundamental absorption edge of the un-doped SnO thin films thus providing tuning effect of the band gap for device applications.

INFLUENCE OF DOPANTS AND DEPOSITION TEMPERATURE ON THE OPTICAL AND SOLID STATE PROPERTIES OF DYE-SENSITIZED NOVEL NANOHYBRID ZnxSnyOz THIN FILMS DEPOSITED USING SPRAY PYROLYSIS

Dye-sensitized Novel Nanohybrid ZnxSnyOz thin films were prepared on glass substrates using spray pyrolysis technique. The dye used is extract from the leaves of tectona grandis. A 0.1M of Zn2+ and 1% was used respectively. Depositions were done at different substrate temperature of 50oC, 100oC, and 150oC. The effect Zn2+ ion and dye extract from tectona grandis leaves on optical and solid state properties of the films were examined and analysed. The result showed that the absorbance of the undoped SnO thin films at various substrate temperatures vary from about 0.1-0.7. The absorbance generally increased with deposition/ substrate temperature exhibiting a maximum for films deposited at 150oC. The average transmittance of both un-doped and Zn2+ doped SnO thin films at 350nm is above 90% regardless of the film thickness. The dye doped samples showed an improvement in optical transmission at 625nm. The reflectance spectra of all films exhibited a similar trend. Peak reflectance was observed at 350nm for un-doped and Zn2+ doped samples of SnO thin films while peak reflectance can be observed at 625nm for dye doped samples. It is also observed that the band gaps of the dye doped samples are lower: 1.55eV- 1.83eV than those of the Zn2+ doped samples: 1.60eV – 2.20eV. This showed that the incorporation of the dye shifted the fundamental absorption edge of the un-doped SnO thin films thus providing tuning effect of the band gap for device applications.

Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer.

A semiconductor under insulator technology in indium phosphide

This letter introduces a semiconductor-under-insulator (SUI) technology in InP for designing strip waveguides that interface InP photonic crystal membrane structures. Strip waveguides in InP-SUI are supported under an atomic layer deposited insulator layer in contrast to strip waveguides in silicon supported on insulator. We show a substantial improvement in optical transmission when using InP-SUI strip waveguides interfaced with localized photonic crystal membrane structures when compared with extended photonic crystal waveguide membranes. Furthermore, SUI makes available various fiber-coupling techniques used in SOI, such as sub-micron coupling, for planar membrane III-V systems.

Ultrathin molybdenum oxide anode buffer layer for organic photovoltaic cells formed using atomic layer deposition

In an organic photovoltaic (OPV) cell, the buffer layers connecting the active photovoltaic material to the electrodes strongly influence the overall energy conversion efficiency. In this work, we demonstrate that a thin layer (<4nm) of MoO3 formed by atomic layer deposition (ALD) of Mo, followed by oxidation in ozone, performs well as an anode buffer layer in organic photovoltaic cells based on a blend of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester. Compared to the commonly used buffer layer poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the MoO3 layer causes virtually no degradation in the transmission spectrum. The improvement in optical transmission leads to higher short-circuit current density, and practically the same power conversion efficiency as OPV cells employing PEDOT:PSS. Results from a substantial number of devices indicate that the improvement is statistically significant, demonstrating the reproducibility and reliability of the layer. Moreover, because of the conformal nature of ALD, this approach can be extended to nanostructured systems.

Improvement in optical transmission of the ambient pressure dried hydrophobic nanostructured silica aerogels with mixed silylating agents

The experimental results on the preparation of transparent and hydrophobic silica aerogels based on ion exchanged sodium silicate (Na 2SiO 3) using mixed silylating agents of trimethylchlorosilane (TMCS), hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDZ) are reported. Hydrogels were prepared with ion exchanged Na 2Si0 3 of 1.10 specific gravity with 1 N ammonium hydroxide (NH 4OH). The resulted gels were exchanged with methanol solvent followed by silylation using HMDZ + HMDSO or TMCS + HMDZ or TMCS + HMDSO mixture in methanol and hexane and dried the gels at room temperature for 24 h, at 50 and 200 °C for 1 h each. It has been observed that the percentage of the silylating agent in the mixture, time interval of addition of one agent followed by another and volume of silylating mixture have an effect on density, % of optical transmission, % of porosity, porevolume, thermalconductivity and refractive index of the aerogels. Hydrophobicity of the aerogels was studied by contact angle measurements. The TMCS + HMDSO aerogels have been found more hydrophobic (contact angle > 150°) than the other aerogels. Further, aerogels have been characterized by pore size distribution, Fourier Transform Infra Red Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and thermogravimetric analysis and differential thermal analysis (TGA–DTA) techniques. It has been found that the weight increase is the highest (325%) for HMDSO + HMDZ aerogels and lowest (1.2%) for HMDSO + TMCS aerogels by keeping the aerogels in the atmosphere over a period of 18 months. Low density (0.042 g/cc) transparent (85%), low thermal conductive (0.047 W/m K), low refractive index (1.0088) and hydrophobic (152°) silica aerogels were obtained with equivolume TMCS + HMDSO mixture of 10 ml, time interval of addition of 12 h between the two reagents prior addition of TMCS followed by HMDSO for 24 h of silylation period. It was found from the TGA–DTA of the aerogels that hydrophobicity of the aerogels remained up to the temperature of 425 °C.

Electrode structure for high transmittance and aperture ratio in TFT-LCD

Abstract In this paper, we propose a new cell structure having a high aperture ratio and transmittance with chevron-shaped electrode. As an exemplary cell, we selected patterned vertical alignment (PVA) mode. Optical transmittance and aperture ratio were calculated by 3D-FEM numerical solver and extended Jones method solver. The simulation results exhibited 4.8% improvement in aperture ratio and 11.3% improvement in optical transmission. Furthermore, in the view of aperture ratio, the aperture ratio of the proposed cell design is 4.8% higher than that of the conventional cell design.

17.2: Invited Paper: Improved PVA Mode with High Transmittance and Aperture Ratio

In this paper, we propose a cell structure which has high aperture ratio and transmittance with chevron-shaped electrode. As an exemplary cell, we selected PVA (Patterned Vertical Alignment) mode. Optical transmittance and aperture ratio were calculated with 3D-FEM numerical solver, TechWiz LCD, which is commercially available. The simulation results exhibited 4.8% improvement in aperture ratio and 11.3 % improvement in optical transmission.

Magneto-optical properties of Y/sub 3-x-y/Ce/sub x/La/sub y/Fe/sub 5/O/sub 12/

Yttrium iron garnet YIG has been characterized extensively for its use in magneto-optic devices, such as optical isolators and magnetic field sensors. The effects of doping cerium and lanthanum into the YIG host are reported. In optical isolator applications operating at 1.31 /spl mu/m and 1.54 /spl mu/m, where miniaturization and temperature stability are important, cerium and lanthanum-containing compositions are considered as alternatives to pure YIG. Measurements were made of the Faraday rotation as a function of temperature, extinction ratio, and saturation magnetization in several garnet compositions. Improvement of optical transmission at 1.31 /spl mu/m and 1.54 /spl mu/m was achieved by the incorporation of small amounts of calcium.