Comparing optical sensing using slab waveguides and total internal reflection ellipsometry

The sensitivity of the effective refractive index of slab waveguide sensors to variations in the refractive index of the cladding is compared to that of the ellipsometric parameters. The changes of the effective refractive index of a waveguide and the ellipsometric parameter\Delta, due to the index change of the cladding, were derived and plotted as a function of the guiding layer thickness and with the index of the cladding. It is found that these changes almost have the same overall feature but the ellipsometric parameters showed considerable higher sensitivity than the effective index of the conventional waveguide optical sensors

Development and construction of rotating polarizer analyzer ellipsometer

A detailed mathematical derivation and an experimental characterization of one to two ratio rotating polarizer analyzer ellipsometer (RPAE) are presented. The alignment, calibration, and testing of reference samples are also discussed. The optical properties of some known materials obtained by the proposed ellipsometer will be shown and compared to accepted values. Moreover, the constructed ellipsometer will be tested using two ellipsometry standards with different thicknesses

Theoretical spectroscopic scan of the sensitivity of asymmetric slab waveguide sensors

An extensive theoretical analysis is carried out to investigate the variation of the sensitivity of optical slab waveguide sensors with the wavelength of the guided wave. We consider a three-layer waveguide as an optical sensor. The sensitivity for both polarizations of light: s-polarized light (TE) and p-polarized light (TM), is derived using the characteristic equation of the structure. The dispersion of the materials is taken into account to study the sensitivity spectroscopic scan over the near IR-range from 1.2–2 µm. It is found that an optimum wavelength exists for each guiding layer thickness and this optimum value increases linearly with the thickness of the guiding layer

Rotating polarizer, compensator, and analyzer ellipsometry

In this paper we propose theoretically a set of ellipsometric configurations using a rotating polarizer, compensator, and analyzer at a speed ratio of N 1 ω: N 2 ω: N 3 ω. Different ellipsometric configurations can be obtained by giving different integral values to N 1, N 2, and N 3. All configurations are applied to bulk c-Si and GaAs to calculate the real and imaginary parts of the refractive index of the samples. The accuracies of all ellipsometric configurations are investigated in the presence of a hypothetical noise and with small misalignments of the optical elements. Moreover, the uncertainties in the ellipsometric parameters as functions of the uncertainties of the Fourier coefficients are studied. The comparison among different configurations reveals that the rotating compensator—analyzer configuration corresponds to the minimum error in the calculated optical parameters

Dye-sensitized solar cells using dyes extracted from flowers, leaves, parks, and roots of three trees

In this paper, eleven natural dyes were collected from three trees and used as photosensitizers for dye sensitized solar cells (DSSCs). The cells were fabricated using TiO2 as a semiconducting layer deposited on transparent fluorine doped tin oxide (FTO) conductive glass using doctor blade method. The absorption spectra of the extracts were performed in the spectral range from 400 nm to 750 nm. The JV characteristic curves of all fabricated cells were measured and analyzed. The parameters related to the solar cell performance were determined. Moreover, the impedance spectroscopy of the cell with the best performance was investigated

Electrical properties of organic light emitting diodes with post fabrication heat and electric field treatments

The current work presents post-fabrication heat treatment and a combined external electric field-heat post-fabrication treatments for organic light emitting diodes (OLEDs). The devices were fabricated in the same run with a standard device without annealing for comparison, with an identical structure of ITO/PVK/Rhodamine B/Pb. After depositing the Rhodamine B layer on the PVK film, the samples were thermally annealed at different temperatures before depositing Pb. Some of the samples were thermally annealed without any external electric field while others were treated by an external electric field during heating. It is found that the annealing temperature of PVK/Rhodamine B layers increases the turn-on voltage of the device. On the other hand, in the electric field-heat treatment, the turn-on voltage is observed to decrease and the maximum current density of the device is dramatically enhanced

Thermoelectricity Based on Cuo as a Semiconducting Material

In this paper, thermoelectricity based on copper(II) oxide CuO as semiconducting material is explored. The electrical properties of the samples were studied under different temperature gradients and pressures. Moreover, the effect of baking temperature was also investigated. CuO prepared using decomposition of Cu(NO3)2 as well as CuO nanopowder prepared using microwave-assisted synthesis technique were investigated and their results were compared. It was found that the current density can be enhanced with increasing the pressing pressure of the sample and when the sample undergoes a baking process. Moreover, it was found that the current density can be considerably enhanced with increasing the temperature gradient between the two ends of the sample. The CuO prepared using microwave-assisted synthesis technique was found to exhibit much better results over those of the CuO prepared using decomposition of Cu(NO3)2

Dyes Extracted from Safflower, Medicago Sativa, and Ros Marinus Oficinalis as Photosensitizers for Dye-sensitized Solar Cells

In this work, three extracts of plant leaves were used as sensitizers for dye-sensitized solar cells (DSSCs). These plants are Safflower, Medicago sativa and Ros marinus oficinalis. The natural dyes were extracted before and after grinding the plant leaves. The UV-VIS absorption spectra of the three extracts in ethyl alcohol solution were measured. The DSSCs were assembled using TiO2 films on Fluorine-doped tin oxide (FTO) coated glass. The DSSCs sensitized with the extracts of grinded leaves showed a better performance compared to those sensitized with un-grinded leaves with the highest efficiency of 0.115 % was obtained for the DSSC sensitized with Medicago sativa. The performance of the DSSCs sensitized with Safflower and Ros marinus oficinalis was significantly improved by acid treatment of the FTO substrates. Impedance spectroscopy of the fabricated cells was also carried out

Natural Dyes as Photosensitizers for Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) were assembled using Zinc oxide (ZnO) nanoparticles as a photoelectrode and natural dyes extracted from eight natural plants as photosensitizers. The structural properties of the synthesized ZnO nanoparticles were studied using XRD, SEM and TEM characterizations. Photovoltaic parameters such as short circuit current density Jsc, open circuit voltage Voc, fill factor FF, and overall conversion efficiency η for the fabricated cells were determined under 100 mW/cm2 illumination. It was found that the DSSC fabricated with the extracted safflower dye as a sensitizer showed the best performance. Also, its performance increased with increasing the sintering temperature of the semiconductor electrode with highest performance at 400 °C. Moreover, it was found that a semiconductor electrode of 7.5 μm thickness yielded the highest response

New Efficient Organic Compounds In Dye-Sensitized Solar Cells

We demonstrate the use of three new organic photosensitizer compounds in dye sensitized solar cells (DSSCs). One of these compounds is a diazapentadiene derivative [1], while the other two compounds are triazole derivatives [1]. The construction of the cell involved use of a commercially available indium tin oxide (ITO) conductive electrode on which a thin layer of TiO2 was deposited by chemical vapor deposition (CVD). The other electrode was composed of a thin graphitic layer on ITO. A gelled iodine/iodide combination was used as the redox system. We have studied the current versus voltage (IV) characteristics and the power versus voltage of these DSSCs at a relatively low light intensity. The efficiency and the fill factor for each cell were consequently calculated