Papers by Keyword: Solar Cell

Abstract: The methods of obtaining the base layers of cadmium telluride to create effective solar cells are considered. At present, two groups of methods are distinguished for the preparation of base layers of cadmium telluride for high-efficiency PECs: low-temperature and high-temperature. If a polyimide film with a temperature stability of 450 °C is used as a substrate, then deposition should be carried out at a temperature of about 430 °C. Therefore, to create base layers of cadmium telluride on a flexible polyimide substrate, it is necessary to use low-temperature methods for producing base layers. It has been established that the formation of base layers of solar cells based on cadmium telluride on flexible polyimide substrates must be carried out by direct current magnetron sputtering.

Abstract: This work deals with the deposited cadmium sulfide (CdS) quantum dots thin films on transparent conductive fluorine-doped tin oxide (FTO) substrates prepared by successive ionic layer adsorption and reaction technique (SILAR). QD deposition based on SILAR is easy, cheap and effective method which improves the surface quality and performance of QD-based devices. The effect of the number of cycles of SILAR on the morphology and size of the quantum dots has been investigated. SILAR technique was adopted for the deposition of CdS on anatase TiO₂ and the three main factors contributing to the performance of QDs processed by SILAR, namely the number of cycles used, the concentration of the precursor solution, and the reaction dipping time, are discussed. The structural, morphological and optical properties were studied using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Raman spectra analysis and UV-Vis NIR analysis, respectively. The particle size of CdS was calculated from XRD pattern using Debye Scherrer’s equation and the calculated particle size was 4.5-9.5 nm. Using CdSQDs, quantum dot sensitized solar cells (QDSSC) were fabricated on FTO substrates as being a transparent conductive oxide. Optical absorption property proved that the band gap energy value was about 2.44 eV. The result delivered from J-V curve revealed that the overall energy conversion efficiency increased with increasing the deposition cycles giving the best efficiency of 2.73 % at 7 cycles.

Abstract: Nd:YAG laser was used at different number of shots (300, 500, and 700 pulse) to prepare ZnO:Cu₂O nanoparticles at mixing ratios of (0.5, 0.7 and 0.9). The optical, structural, morphological and electrical properties of the prepared films were investigated. The energy band gap was found to be (2.5, 3.2 and 3.53 e.v). The crystalline structure showed no impurity peaks indicating that the final product was free from surface impurities. Also, the materials peaks and intensity is present and well identified as the mixing ratio varies. The AFM results for all ratios indicate that as the number of pulses increase, the higher the resulted grain size. The average grain size was between (58.82 nm) to (95.75nm). The J-V characteristics were measured for the prepared solar cells and it was found that the efficiency varied with the mixing ratio and film thickness from 0.29% to 2.38%. F.F varied from 0.28 to 0.25.

Abstract: Titanium dioxide (TiO₂) nanoparticles thin film has been successfully prepared by a simple hydrothermal process using Hydrochloric Acid (HCl) as chelating agent and Titanium (IV) Chloride (TiCl₄) as precursor. In this study, the nanostructured TiO₂ thin films were prepared at different hydrothermal reaction times of 2 hours, 5 hours, and 10 hours, and then Ag₂S Quantum Dots (QDs) were deposited on the surface of TiO₂ nanoparticles using 6 cycles of Successive Ionic Layer Adsorption and Reaction Deposition (SILAR) method. The surface morphology, crystalline structure and optical characterizations of the films were carried out using Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscope (AFM), X-ray Diffraction (XRD) and Ultra-Violet-Visible Near Infrared Spectrophotometer (UV-Vis). For electrical properties, four-point probe investigated the sheet resistance, resistivity, and conductivity of these thin films. TiO₂ nanorods were formed with diameter ranged from 33.78 nm to 42.58 nm and the length of TiO₂ layer increased as the reaction time increased, from 2.84 μm to 3.93 μm (without Ag₂S QDs) and 2.88 μm to 4.85 μm (with Ag₂S QDs). When the reaction time reaches 10 hours, nanoflowers can be seen on the surface of film. The XRD results showed that with longer reaction time, the value of full-width at half maximum (FWHM) of the TiO₂/ Ag₂S QDs thin films decreased from 0.335° to 0.263 while the crystallite size increased from 22.73 nm to 35.39 nm. UV-Vis analysis indicated that the optical band gap of these thin films decreased from 2.68 eV to 2.00 eV (direct) and 2.94 eV to 2.40 eV (indirect) with increased in reaction time. The electrical properties of the films showed that the resistivity varied between 7 x 10⁷ Ω.cm and 5.07 x 10⁷ Ω.cm when the reaction time changed from 2 hours to 10 hours. The conductivity of the TiO₂/ Ag₂S QDs thin films increased with the increase in hydrothermal reaction time and further increased with the incorporation of Ag₂S QDs. Besides, the TiO₂ films synthesized hydrothermally for 10 hours showed higher surface roughness as compared to other thin films. The obtained results showed that the TiO₂ / Ag₂S QDs thin films are applicable as a photoanode for Quantum Dots Sensitized Solar Cell (QDSSCs) applications.

Abstract: The article contains a description of various growing conditions for isoparametric heterostructures based on InP. It is shown that the structural perfection of solid solutions grown on InP substrates is influenced by parameters, such as the temperature of the epitaxy process, the temperature gradient, and the composition and thickness of the liquid zone. By analyzing the quality of the surface and the structural perfection of isoparametric AlGaInAsP solid solutions, based on InP, optimal parameters of the zone recrystallization process in the temperature gradient field (TGZR), at which the epitaxial films had minimal roughness and high crystalline perfection, were found.

Abstract: For Visible Light Communication (VLC) systems, photo receiver is very important for obtaining low noisy modulated signal at receiver side since the pure modulated signal is easy demodulated. Therefore, we give a comparison of performance of three type photo receivers in this paper. In first application, we use a photoresistor to detect the modulated signal. It is referred as CDS (cadmium-sulfide) resistor. Another detector is solar cell unit. The other receiver is selected photodiode detector. It is shown from experimental results that the most appropriate modulated signal is obtained at output of photodiode. The output of solar cell consists of very complex signal compared with output of photoresistor. Additionally, we use PPM (Pulse Position Modulation) technique for transmission of data signal.

Abstract: The vertically aligned TiO₂ Nanotubes (TiNTs) extracts electrons from an absorber and also helps in its transport in perovskite and dye sensitized solar cells (DSSCs) solar cells. Thus electron transporting layer plays a very important role in photon to electron conversion. Electrochemical anodization is been used widely to grow TiNTs for solar cell applications; due to its low cost, flexibility to vary pore diameter and tube length. We observed that, TiNTs maintained its tubular array only for a set time period. On increasing the growth time they begin to take the form of nanocrystals with {001} facets. Formation of these titanium nanocrystals (TiNcs) was clearly observed through field emission scanning electron microscope (FESEM) and Transmission electron microscopy (TEM). Thus TiO₂ nanostructures can be tuned by varying anodization time. More importantly, optimization of the reaction process led to the growth of more orderly, crystalline anatase TiNTs/TiNcs over Ti metal foil substrate. The crystal structure and surface morphology of the prepared thin film samples were studied using X-ray diffraction (XRD) technique and scanning and transmission electron microscopes (TEM). XRD confirmed the anatase phase of as grown TiO₂ with (101) as major intensity preferred orientation. Lattice parameters calculated were found to be a= 3.77-to-3.82 and c= 9.42-to-9.58 for grown TiO₂.

Abstract: Photovoltage formation across Si and GaAs p-n junctions exposed to laser radiation is experimentally investigated. When the photon energy is lower than semiconductor forbidden energy gap, the photovoltage is found to consist of two components, U=U_f+ U_ph. The first one Uf is fast having polarity of thermoelectromotive force of hot carriers. The second one Uph is slow component of opposite polarity, and it is caused by electron-hole pair generation due to two-photon absorption. Uph was shown to decrease with the rise of radiation wavelength due to diminution of two-photon absorption coefficient with wavelength. Predominance of each separate component in the formation of the net photovoltage depends on both laser wavelength and intensity.

Abstract: Vertically aligned nanorods ZnO have been deposited hydrothermally on the pre-coated ZnO seeded-glass substrates. Enhanced vertical alignment is achieved as a result of combined film post-treatments. Dipped-drawn and immersed-washing the as-synthesized ZnO films in water as well as quenching of the hydrothermal were proposed to hinder excessive deposition and engineer the growth of ZnO nanorods. The XRD patterns shows suppressed growth of ZnO crystallite along (101) with increased textural coefficients on (002), TC₀₀₂, from 3.94 to 5.23. Dense vertically aligned bundles of ZnO nanorods may reach up to 0.75 μm length. Bandgap energy of the resulted ZnO nanorod thin films were ranging from 3.69 to 3.79 eV, wider than those of bulk ZnO. Hydrothermal technique with simple post-treatments of immersed-washing and hydrothermal quenching has offered robust and efficient method to prepare vertically-aligned 1-D ZnO nanorods potential as photoanodes for dye-sensitized solar cells.

Abstract: Electrochemical etching was carried out to produce porous silicon based on crystalline silicon n-type (100) and (111) wafers. Etching times of 10, 20, and 30 min were applied. Porous silicon layer was used as anti-reflection coating on crystalline silicon solar cells. The optimal etching time is 20 min for preparing porous silicon layers based on crystalline silicon n-type (100) and (111) wafers. Nanopores with high porosity were produced on the porous silicon layer based on crystalline silicon n-type (100) and (111) wafers with average diameters of 5.7 and 5.8 nm, respectively. Average crystallite sizes for the porous silicon layer based on crystalline silicon n-type (100) and (111) wafers were 20.57 and 17.45 nm at 20 and 30 min, respectively, due to the increase in broadening of the full width at half maximum. Photoluminescence peaks for porous silicon layers based on crystalline silicon n-type (100) and (111) wafers increased with growing porosity and a great blue shift in luminescence. The minimum effective coefficient of reflection was obtained from porous silicon layers based on the crystalline silicon n-type (100) wafer compared with n-type (111) wafer and as-grown at different etching times. Porous silicon layers based on the crystalline silicon n-type (100) wafer at 20 min etching time exhibited excellent light trapping at wavelengths ranging from 400 to 1000 nm. Thus, fabricated crystalline silicon solar cells based on porous silicon (100) anti-reflection coating layers achieved the highest efficiency at 15.50% compared to porous silicon (111) anti-reflection coating layers. The efficiency is characterized applying I-V characterization system under 100 mW/cm² illumination conditions.