Transmittance and Extinction Coefficient of Sea and Well-Water in Mombasa County, Kenya

Using a laser transmitter in the range of 200 nm to 1200 nm, transmittance and total extinction coefficients were determined for two different but close related optical media which are ocean water and shallow well water in Mombasa County, in Kenya. The results were interpreted using Lambert–Beer’s law as applied for very small ranges of concentrations. It was established that the total extinction coefficients for two forms of water showed linearity with values of total extinction coefficients found to be µt = 7.734 (g/ml)-1 mm-1 and µt = 127.6 mm-1 at a wavelength of 638 nm for ocean water and shallow well water respectively

Modeling a Bandwidth of a Two-Level Independent Quantum Laser System States

An electromagnetic radiation is basically considered to be a transverse wave propagating through an accessible media whether it is an optical fibre or a thin film depending on its propagating conditions. In analyzing its propagation, utilized specific cross-section areas have become an important base of understanding its extinction parameters. The term cross-section in this work applies only to boundary conditions within which particles interact within electromagnetic spectra through absorption or scattering. In such small volume contextual framework, nanotechnology reconsiders scattering cross-section coefficients. In this work, two different degenerate states were modeled and analyzed using a developed model of a laser cavity containing a media of length, L, with a gain of, k, per unit length which were mirrored to represent the upper and a lower level manifolds inhomogeneous broadening Stark levels respectively. The model developed created an impression that a laser medium is a coherent ensemble of particles or atoms whose bandwidth depends on how a laser is constructed

Effect of TiO2 Compact Layer on DSSC Performance

Dye-sensitized solar cells offer an economically reliable and suitable alternative in moderating the challenges presented by the existing convectional photovoltaic cells. Whereas, for convectional solar cells the semiconductor adopts both the duty of light absorption and charge carrier transport, these two functions are separated in dye-sensitized solar cells. However, the efficiency of dye-sensitized solar cells has remained relatively low. For this reason, this research was aimed at how to increase the dye-sensitized solar cells performance. To achieve this, compact cover of TiO2 was deposited on a conductive glass substrate by using Holmarc’s Spray Pyrolysis system, using Ultrasonic Spray Head and spraying in vertical geometry, while TiO2 nanoparticles and nanotubes were deposited by screen printing technique on top of a transparent conducting FTO glass slide with or without the TiO2 compact layer. Transmission characteristics showed that introducing TiO2 compact layer on the conductive film lowers the transmission while reflectance properties were less than 15 % for all the prepared thin films. SEM micrographs showed that TiO2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together to form a large surface area film. Solar cell performance properties revealed that introducing compact layer to dye-sensitized solar cells improved the performance by 145 % (from 1.31 % to 3.21 %) while TiCl4 treatment on compact layered dye-sensitized solar cells increased the efficiency by 28.79 % (from 0.66 % to 0.85 %)

TiO2 Thin Films by Solution Technique for Solar Cells

Titanium dioxide has a number of applications in solar cells. In this study, TiO2 thin films were synthesized using a simple but less expensive, low temperature and large area deposition method referred to as chemical bath deposition. Their electrical and optical properties were examined at various temperatures where it was observed that the films exhibited low reflectance which increased with increase in wavelength with refractive indices of 2.2–2.5 in the visible spectra. Sheet resistivity ranged between 13.54±0.095 Ω/m to 17.27±0.209 Ω/m. They were use to fabricate photovoltaic cell which exhibited the following parameters: a short circuit current, Isc=0.002445 A, open voltage, Voc = 0.04731 V, a fill factor, FF=0.551 and an efficiency, η=0.531 %. They were recommended for diode applications

Electrical Behavior of Cd0.3Zn1.1x S0.7 Thin Films for Non-Heat Light Emitting Diodes

In developing countries like Kenya, solution processing technique is the cheapest and simplest technique to grow inorganic composites thin films. This method was used to grow thin films of Cd0.3Zn1.1xS0.7on ordinary microscope Perspex substrate slides from aqueous solutions of Zinc chloride and cadmium chloride in ammonia solution. A solution of triethanalomine was used as a complexing agent while thiourea was used as source of sulphide ions. Electrical properties as a function of their thicknesses were obtained by varying deposition time while all other parameters were maintained constant. Using a resistance measurement device and a Gauss meter, resistivity and the conductivity of the films were found to be thickness dependent with semiconductor nature

Effect of Surface Passivation on CdxNi1-xS Thin Films Embedded with Nickel Nanoparticles

Certain treatments done to binary CdS, such as incorporating Ni onto CdS produces ternary thin films may cause major optical parameters that have a number of applications including for solar cell device fabrication. In this paper, we report on the effect of surface passivation on the band gap and other related optical properties of CdNiS thin films. Thin films for CdxNi1-xS were prepared on glass substrates by chemical solution method. Effects of surface passivation and variation of the volume of nickel ions on the optical properties CdS hence obtaining CdxNi1-xS thin films was investigated. It was observed that the thin films hard an average Transmittance above 68 %, with reflectance below 25 % across UV-VIS-NIR region. A plot of (αhν) 2 versus hν gave energy band gap between 2.55–3.49 eV for as-grown samples and 2.82–3.50 eV for annealed samples. The passivated samples had band gap energy values within the range 2.85–3.12 eV. It was concluded that an increase in concentration of Cd2+ and Ni2+ ions in the reaction led to an increase the band gap while optical conductivity ranged between 3.78x1011–2.40x1012 S-1

Optical Properties and Analysis of OJL Model’s Electronic inter-band Transition Parameters of TiO2 Films

Titanium dioxide is a wide band gap semiconductor responsible for the bright white appearance in most substances. This material has many unique properties due to its extra-ordinary chemical stability. TiO2 has a conduction band that closely matches the excited energy level of organic dyes hence it is used in fabrication of photo-anode electrode of dye sensitized solar cell. However, the optical properties and the density of states of TiO2 thin films determine the performance of dye sensitized solar cell fabricated from TiO2 photo-anode electrode. For this reason, the purpose of this study was to investigate the optical properties and the OJL electronic inter-band transition analysis of TiO2 nanoparticle thin films. Under the OJL model, the expressions of density of states were specified for the optical transition from the valence band to the conduction band. The TiO2 nanoparticles were prepared using sol-gel and hydrothermal methods and deposited on a conductive glass substrate by screen printing and spray pyrolysis techniques. SEM analysis revealed that TiO2 nanoparticles were spongy and had unevenly sphere-shaped profile while TiO2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together. This study showed that TiO2 thin films have both direct and indirect band-gaps. The OJL Gap energy (E0) values were observed to be between 30273.2356 and 31072.0000 wavenumbers which translated to band-gap energies between 3.744 and 3.843 eV. From these findings showed that TiO2 films prepared could be used in the fabrication of high performing dye-sensitized solar cell

Synthesis and Characterization of Natural Sensitizers for Dye Sensitized Solar Cells

Natural dyes of anthocyanin extract from flame tree flower (Delonix regia) and chlorophyll extract from pawpaw leaf (Carica papaya) were used as sensitizer to fabricate dye sensitized solar cell (DSSC). The photoelectrode were subjected to UV/Vis spectrophotometer to view their absorbability. The photo electrochemical performances of DSSCs obtained from I.V characteristics showed conversion efficiency, (ɳ) of 0.80 % for the dye extracts from flame tree flower (anthocyanine), with open-circuit voltage (VOC) of 0.5249 mV, short-circuit current density (Isc) of 44.6191 mA/m2 and Fill factor (FF) of 0.5837. Chlorophyll dyes extract from pawpaw leaf has VOC, Isc, FF and conversion efficiency, (ɳ) of 0.5249 mV, 16.5283 mA/m2, 0.5585 and 0.27 % respectively. The conversion efficiency for the mixed dyes (anthocyanin and chlorophyll) at ratio 1:2 is 0.23 % with VOC, Isc and FF of 0.5500 mV, 14.2750 mA/m2 and 0.5451 respectively, while the dye mixture at ratio 1:4 achieved VOC of 0.5249 mV, Isc of 18.4941 mA/m2, FF of 0.5206 and conversion efficiency (ɳ) of 0.26 %. Anthocyanine from flame tree flower dye extract had the higher conversion efficiency of 0.8 % which could be better in term of application in dye solar cell

Choosing a Better Delay Line Medium between Single-Mode and Multi-Mode Optical Fibers: the Effect of Bending

Optical fiber cables are materials whose core is made of silica and other materials such as chalcogenide glasses; they transmit a digital signal via light pulses through an extremely thin strand of glass. The light propagates and is being guided by the core which is surrounded by the cladding. Light travels in the optical fiber in the form of total internal reflection in the core of the fibers. The flexibility, low tensile strength, low signal loss, high bandwidth and other characteristics of optical fibers favors it for use as a delay medium in many applications. Another favorable characteristic of optical fiber delay lines is are their relative insensitivities to environmental effects and electromagnetic interferences. The immunity of optical fibers to interferences and their less weight added advantages to it for use as delay medium. Single-mode and multi-mode are the two most popular types of optical fibers. Single-mode fibers have good propagation and delay properties with a minimal loss that allows the signal to propagate in a large distance with insignificant distortion or attenuation. The percentage of power transmission of single-mode fibers is found to be higher than that of the multi-mode fibers. It is, therefore, a preferred type for use as a delay line. In this paper, relative studies of the two optical fibers modes, and the results of power input/output measurement of the two modes are presented with a view to coming up with a better type for use as a delay medium

Studies on Cd1Se0.6Te0.4 Thin Films by Spectroscopic and Diffractometer Characterization

Cadmium selenide tellurium is a compound containing cadmium, tellurium and selenium elements forming a combined solid. Hall measurements suggest that it is an n-type semiconductor. Related optical studies indicate that is transparent to infra-red radiation. Structural studies clearly show that it has a wurtzite, sphalerite crystalline forms. Cadmium is a toxic heavy metal, and selenium is only toxic in large amounts or doses. By this toxicity, cadmium selenide is a known to be carcinogen to humans; however, this does not stop investigating it for optoelectronic applications. Current research has narrowed down to investigating cadmium selenide when in the form of nanoparticles. Cadmium selenide finds applications has found applications in opto-electronic devices like laser diodes, biomedical imaging, nano-sensing, high-efficiency solar cells and thin-film transistors. By chemical bath deposition, Cd1Se0.6Te0.4 thin films were grown onto glass. Tellurium was gradually introduced as an impurity and its crystalline structure and optical properties were investigated by XRD and UV-VIS spectroscopy. The main Cd1Se0.6Te0.4/glass characteristics were correlated with the conditions of growing and post-growth treatment and it was found out that films were homogeneous films with controllable thickness onto the glass substrate and suitable for n-type “sandwich” heterostructures applications. Comparison of the intensities of equivalent reflexions provided a test for the internal consistency of the measurements. Equivalent reflexions in two specimens differed on average by 1.4 % and 0.6 % from the mean measured intensity, attesting to the high internal consistency of measurements from extended-face crystals. By comparison from data obtained from all samples showed their average deviation from the mean to be 0.9 %