A number of models have been developed to describe electron transfer between electrolytes and group II-VI binary semiconductors. In this report, a study was conducted to describe and model electron transfer between an inorganic semiconductor, (i.e. CdS) and a ferric oxidizing/reducing agent [i.e. K3Fe(CN)6/K4Fe(CN)6]. We describe the interfacial electron transfer using the semi-classical theory approaches as described by Marcus and later developed by Gerischer and therefore called Gerischer model as it is applied to heterogeneous electron transfer in a semiconductor -electrolyte interface. CdS thin films were grown by electro-deposition method on the indium tin oxide (ITO) substrates and were used as electrodes. The data collected was used to determine the kinetic constant rates and re-orientation energies as measured in the solutions with different concentration of redox system, Fe +3 / Fe +2 . Experiments showed that when concentration of oxidized species increased and causing an increase in 2 , F redox E activity, the kinetic constant rates decreases inversely. Equally light induced current at 0.0V/Ag was higher when the ratio of the oxidant-reductant (i.e. 2/0.02 and 0.2/0.02) was high. EIS studies revealed that for the two ratios of. 2/0.02 and 0.2/0.02, the difference of current density was comparable to the transfer of the charge carriers for the oxidant-reductant electrolyte at 2/0.02 with respect to 0.2/0.02.
Abstract. Planck's constant is named after Max Planck, a nineteenth-century physicist who first described it by relating it as E=h usual meanings. It is a relationship used when comparing a quantum of energy absorbed to that emitted during electron transitions which can be extended to emission by light-emitting diodes. The purpose of this study was to determine Planck's constant using the energy needed to excite free electrons in a light emitting diode. When a light-emitting diode is switched on, electrons recombine with holes within and release energy in the form of photons which can be determined using energy band gaps of the semiconductor composite material used to fabricate the LED. Therefore, LEDs consist of a chip of doped semiconducting layers to create a p-n junction. In LEDs, current flows easily from the p-side to the n-side but not in the reverse from electrodes with different voltages. When an electron meets a hole, it is inhaled and it falls into lower energy level releasing energy in the form of a photon. Photon emissions take place when electrons return to a lower energy state. Therefore, electrons within a LED crystal are excited to a higher energy state and any radiation emitted depends on the p-n junction direct band gap. Depending on the materials used, LEDs emit radiation with energies corresponding to either near-infrared, visible, or near-ultraviolet light. In reality, a LED is designed to have a small area (approximately less than 1 mm 2 ). In this work, an electric current was used to excite electrons and the corresponding energy was measured using a voltmeter. Planck's constant was calculated by substituting the obtained frequency and energy from the voltmeter in the relationship, E = h.
In this article, we present a theoretical study on localized surface Plasmon of spherical Ag nanoparticles (NPs) done by numerical simulation. A plane EM wave was used to determine absorption cross-section and results showed that excitation of LSPPs produced an electric field on the surface of the nanoparticle. This field causes a large cross sectional area that influences higher scattering of incident photon at the surface of an absorber layer. It was concluded that LSPPs excitations in small size spherical particles can be utilized in low-cost solar cells to increase PCE of solar panels and can be expanded to many other fields of optoelectronic technologies ranging from solar cells, through photo diodes to optical bio-sensing applications.
Abstract. Methyl ammonium lead tri-iodide hybrid thin films were grown using solution technique. They were doped with silver nano-particles at different concentrations at concentrations of 0.05, 0.06, 0.07, 0.08, and 0.09 mM. Their reflectance and transmittance were recorded in the wavelength range 300-900 using UV-Vis double -beam spectrophotometer. Using these measurements, other optical parameters were simulated using scout software. The effect of silver nanoparticles was investigated. Results revealed that the thin films had highest transmittance of about 79 % as their band gap varied from 1.921-1.832 eV. Electrical conductivity varied from 1.4-1. . It was concluded that the thin films were suitable for photonic device applications.
In thin film nano-crystals studies, electron energy levels are known not continuous in the bulk thin films but are rather discrete(finite density of states) because of confinement of their electron wave functions to the physically dimensions of the particles. This phenomenon is called Quantum confinement and therefore nano-crystals are also referred to Quantum dots. The quantum confinement effect is mainly observed when the size of the particle involved is too small to be comparable to the wavelength of the electron. To understand this effect, this study broke the words confinement to mean to confine the motion of randomly moving electron to restrict its motion in specific energy levels (discreteness) and the term quantum to reflect the atomic realm of particles involved in this study. So as the size of a particle decrease to a nano scale, then the decrease in confining dimension causes the particle energy levels to be too discrete and at the same time widens up the band gap. As a result the ultimately effect is that the band gap energy increases. In this study, nanocrystalline tin sulphide (SnS) powder was prepared using tin chloride (SnCl2) as a tin ion (Sn+2) source and sodium sulfide (Na2S) as a sulfur (S-2) ion source using solution magneto DC sputtering technique. The as-synthesized thin film in form of nanoparticles were then qualitatively and quantitatively analyzed and characterized in terms of their morphological, structural and optical properties and found to have an orthorhombic structure whose direct band gap had blue shifted (1.74 eV) and was confirmed using theoretical calculations of exciton energy based on the potential morphing method (PMM) in the Hartree Fock approximation.
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.
Abstract. Cadmium selenide tellurium is a compound containing cadmium, tellurium and selenium elements forming a combined solid. Hall measurements suggest that it is an ntype 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, Cd 1 Se 0.6 Te 0.4 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 Cd 1 Se 0.6 Te 0.4 /glass characteristics were correlated with the conditions of growing and postgrowth 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 %.
Abstract. 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 Cd x Ni 1-x S 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 Cd x Ni 1-x S 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 Cd 2+ and Ni 2+ ions in the reaction led to an increase the band gap while optical conductivity ranged between 3.78 10 11 -2.40 10 12 S -1 .
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