Theoretical modeling of a new structure of III-V tandem solar cells by using parabolic trough concentrator

In this study, potential efficiency of GaInP/GaAs mechanically stacked two-junction solar cell is theoretically investigated by optimizing the thickness of GaAs and GaInPandusing a new optical model to separate the junction between the two solar cell in order to solve problems of tunnel junction and difficulties of fabrication. The principal of this new model is inspired from that of parabolic trough concentrator. Results show that the optimum conversion efficiency is 43 % under AM1.5 spectral illuminations. The obtained results from computation and Matlab simulation of three fundamental parameters which are Reflectance R, external quantum efficiency QE and current density J, would be helpful in designing and fabricating high efficiency GaInP/GaAs mechanically stacked solar cell in experiment.Keywords: GaInP/GaAs; parabolic trough concentrator; optical model; AM1, 5 illuminatio

Yttrium oxide passivation of porous silicon for improved photoluminescence and optoelectronic properties

This paper reports on the effect of yttrium oxide as a novel treatment to improve the photoluminescence intensity and stability of porous silicon (PS). Yttrium oxide (Y2O3) was incorporated into the PS layers by impregnation method using a saturated aqueous solution. The penetration of Yttrium into the PS microstructure was examined using the Energy Dispersive X-ray spectrometry (EDS) and the Backscattered Electron Detector (BED-C) for composition imaging and analysis. The morphology of the front surface was studied using a Field Emission Scanning Electron Microscope (FESEM). The deposited yttrium oxide onto the PS layers was thermally activated to passivate efficiently the silicon dangling bonds, and prevent the porous silicon from huge oxidation. The photoluminescence (PL) peak intensity of impregnated PS was increased noticeably compared to the as-prepared untreated PS. Unlike the as-prepared PS photoluminescence dependence with aging, the yttrium-passivated PS layers PL peak shows no shifts during aging allowing a high stability. Furthermore, we obtained a significant improvement of the effective minority lifetime (Teff) after a short anneal at 600 °C, while increasing the temperature reduces noticeably the passivation properties. The improved surface passivation experienced after the thermal annealing can be ascribed to yttrium diffusion into the PS layer, with a resulting redistribution of yttrium oxide and subsequent passivation of silicon dangling bonds in the sub-interface region, this was confirmed by EDS analysis. The internal quantum efficiency (IQE) measurements were performed to study the optoelectronic properties of the processed monocrystalline silicon substrates

Photothermal Deflection Spectroscopy Study of Nanocrystalline Si (nc-Si) Thin Films Deposited on Porous Aluminum with PECVD

We have studied the optical properties of nanocrystalline silicon (nc-Si) film deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure using, respectively, the Photothermal Deflection Spectroscopy (PDS) and Photoluminescence (PL). The aim of this work is to investigate the influence of anodisation current on the optical properties of the porous aluminum silicon layers (PASL). The morphology characterization studied by atomic force microscopy (AFM) technique has shown that the grain size of (nc-Si) increases with the anodisation current. However, a band gap shift of the energy gap was observed

Genetic diversity in Tunisian horse breeds

This study aimed at screening genetic diversity and differentiation in four horse breeds raised in Tunisia, the Barb, Arab-Barb, Arabian, and English Thoroughbred breeds. A total of 200 blood samples (50 for each breed) were collected from the jugular veins of animals, and genomic DNA was extracted. The analysis of the genetic structure was carried out using a panel of 16 microsatellite loci. Results showed that all studied microsatellite markers were highly polymorphic in all breeds. Overall, a total of 147 alleles were detected using the 16 microsatellite loci. The average number of alleles per locus was 7.52 (0.49), 7.35 (0.54), 6.3 (0.44), and 6 (0.38) for the Arab-Barb, Barb, Arabian, and English Thoroughbred breeds, respectively. The observed heterozygosities ranged from 0.63 (0.03) in the English Thoroughbred to 0.72 in the Arab-Barb breeds, whereas the expected heterozygosities were between 0.68 (0.02) in the English Thoroughbred and 0.73 in the Barb breeds. All FST values calculated by pairwise breed combinations were significantly different from zero (p  <  0.05) and an important genetic differentiation among breeds was revealed. Genetic distances, the factorial correspondence, and principal coordinate analyses showed that the important amount of genetic variation was within population. These results may facilitate conservation programs for the studied breeds and enhance preserve their genetic diversity

Enhancement of porous silicon photoluminescence using vanadium pentoxide (V 2

A new method has been developed to improve the photoluminescence intensity of porous Silicon PS. In this treatment we used vanadium, for the first time, to passivate porous silicon. Thermal evaporation of (V2O5) onto PS layer, followed by a thermal treatment at 100°C, 200°C, 300°C and 400°C for 15 min under oxygen flow, can increase the intensity of the photoluminescence of PS. Vanadium oxide covers the nanoparticles of silicon without changing the wavelength distribution of the optical excitation and emission spectra. Changes in the surface morphology induced by thermal treatment were investigated by atomic force microscope (AFM) showing an increase of the nanoparticles dimensions compared to the initial dimensions of the PS nanostructure. The reflection spectra of PS, before and after treatment with (V2O5), performed in the 300–1200 nm wavelength range and compared to a virgin mc-Si wafer, showed an important decrease of the reflectivity by this new treatment

Impurity removal process for high-purity silica production by acid leaching

In our days obtaining silica sand with very high purity is a primordial stage in photovoltaic industry. The effects of acids on the removal of impurity from silica sand have been studied using leaching acids: mixture composed of HF/HCl/H2O with a volume composition of (1:7:24).The obtained material was characterized using Ultraviolet-Visible absorbance (UV-Vis) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Results of the application of this technique show a significant reduction of the amounts of undesirable impurities present in natural silica (such as Co, Fe, Ca, Al, Mg …)

Effect of the temperature and the porosity of the gettering process on the removal of heavy metals from Tunisian phosphate rock

Gettering is a process by which unwanted impurities are removed by providing an alternative location, this method used by many researchers for the purification of silicon wafers or powder. In this work, this method is used for the first time to remove the impurities from Tunisian phosphate rock (TPR). This method consists in two steps: the rapid thermal processing by infrared furnace followed by a rapid chemical etching. In order to enhance the efficiency of this process, a porous layer on the surface of grains was grown. By this method, we have demonstrated in this present work that the majority of impurities were well extracted from TPR. UV–visible absorption spectra show that the highest intensity of absorbance (∼1) appears for the porous sample treated at 900 °C (P900 °C), which due to the presence of large quantities of impurities in the extracted solution. These results were well confirmed by AAS and ICP-AES which show that the majority of the impurities have been almost removed for the P900 °C sample. Keywords: Gettering process, Porous phosphate rock, Temperature, Impuritie

Origin of the photoluminescence shifts in porous silicon

The origin of the photoluminescence (PL) shifts in Porous Silicon (PS) is discussed according to a quantum confinement – based model, in which we modelize the PS layer as a mixture of quantum dots and wires. It was shown that a PL blueshift or redshift may occur during laser irradiation of PS, depending on preparation conditions. No PL shift was observed for some PS samples, even after a long ageing in air, due to the presence of an amorphous silicon phase detected from Raman spectroscopy measurements. It was found that the presence of the amorphous phase plays an important role in the PL behaviour of oxidised PS