Résumé: Undoped and Ni-Eu co-doped ZnO thin films were successfully fabricated via spray pyrolysis at 400°C. The impact of co-doping on the structural, morphological, electrical, and optical properties of the thin films was thoroughly investigated. X-ray diffraction (XRD) analysis confirmed the absence of secondary phases and verified the successful incorporation of dopant ions into the ZnO lattice. Morphological examination revealed enhanced crystallization and a more uniform surface following the incorporation of nickel. Spectral studies in the UV-Vis region were conducted to determine the optical band gap of the synthesized ZnO films, indicating a slight decrease in bandgap values and volume and surface energy losses (VELF and SELF) with increasing Ni doping concentration. Photoluminescence spectra exhibited emission peaks in the UV region around 415 nm and broad visible emissions spanning 450-650 nm for all samples. Electrical characterization using Hall Effect measurements confirmed n-type electrical conductivity in all prepared films, as evidenced by the observed negative Hall coefficients. The co-doped ZnO thin films, particularly those incorporating Ni-Eu, show promise for applications in electronic and optoelectronic devices. Additionally, we investigated the photodegradation of green malachite under a UV lamp. Remarkably, the results demonstrated degradation rates of 93% within 2 hours, showcasing promising potential for practical applications.

Résumé: The polycrystalline silicon (poly-Si) thin films are widely used in photovoltaic applications. However, the main drawback is the electronic activity of the grain boundaries which affects the performance of solar cells based on this material. In order to reduce the impact of this phenomenon, which affects the photovoltaic conversion efficiency, heat treatments before doping and annealing under hydrogen were carried out on phosphorus-doped poly-Si thin films. The obtained results showed that the heat treatments before doping allow an improvement in the free carriers concentration of 15 to 55% for temperatures ranging from 1000 to 1150 °C. In addition, an increase in the carriers mobility and a reduction in the resistivity of the studied thin films were observed. On the other hand, the annealing under hydrogen allowed an improvement of 10 to 18% on the free carriers concentration, a reduction of the resistivity, and an increase of the carriers mobility. Therefore, it can be deduced that heat treatments followed by annealing under hydrogen allow the passivation of the grain boundaries and thus lead to an improvement of the electrical characteristics, and consequently, the efficiency of solar cells made from poly-Si thin films.

Résumé: In this study, for the concentrations of x=0.0, 0.25, 0.5, 0.75 and 1.0, the calculations of the physical properties of GaP1–xNx mixed alloys are presented. To perform these calculations, we employ WIEN2k computational code based on the approach of full-potential linearized augmented plane wave plus local orbital FP(L(APW?lo)), which is framed within density functional theory. At first, at the level of the WC-GGA scheme, the phase stability of the GaP1–xNx alloys in their sodium chloride (B1), zinc-blende (B3) and wurtzite (B4) structures were analysed. The analysis of our results shows that GaP, GaP0.75N0.25, GaP0.5N0.5 and GaP0.25N0.75 are stable in B3 crystal structure, whereas GaN is found to be stabilized in wurtzite structure. Moreover, for each concentration, the pressure-induced phase transition of B3 and B4 structures to B1 structure is also explored. On the other hand, the calculations of the band structures show changeover of indirect band gap energy for GaP with energy gap 2.23 eV to direct band nature for GaN with band gap energy 3.183 eV. Likewise, the optical properties are explored for the energy range of 0.0–40 eV. The investigations of the thermodynamic properties, for example, entropy, Debye temperature, specific heat are carried out at the level of the ‘quasi-harmonic Debye model’. Moreover, the effect on the thermodynamic properties by temperature and pressure is also predicted. The results obtained for band gap energy as well as the optical absorption coefficients endorse that the investigated compositions of the alloys are very right for infrared to visible region optoelectronic applications.

Résumé: With their high absorption coefficient, the CuIn1- xGaxSe2 chalcopyrite-structured compounds have a number of advantages in the race to produce large-scale, low-cost solar panels. In this perspective, CuIn1- xGaxSe2 ingots (x = 0.3, 0.4, 0.5) were prepared, and the influence of the proportion of gallium on the structural, optical, and electrical properties was studied. X-ray diffraction analyzes have shown that the obtained ingots are polycrystalline and possess a chalcopyrite structure. The preferred orientation along the plane (112) which is very suitable for photovoltaic conversion has been obtained. The main X-ray diffraction peaks showed changes in their diffraction angles that increased with increasing gallium proportion. The ratio “c/a” calculated from the lattice parameters “a,” and “c” was found close to two for all gallium proportions. Spectrophotometer analysis allowed us to observe the good absorption of the compound CuIn1- xGaxSe2, and the obtained results showed that the band gap width Eg increases with the increase in the proportion of gallium and was found to vary between 1.12 eV and 1.32 eV, with Eg = 1.26 eV for x = 0.4. Characterizations by Hall effect measurements showed that the produced ingots have a p-type conductivity. Also, a low resistivity of the order of 0.76 Ωcm was found for x = 0.4. The results obtained in the context of this work show that the prepared CuIn0.6Ga0.4Se2 compound exhibits the best optoelectronic properties.

Résumé: Due to increased energy intensive human activities resulting in accelerated demand for electric power coupled with the occurrence of natural disasters with increased frequency, intensity, and duration, it becomes essential to explore and advance renewable energy technology for the sustainability of the society. To meet the energy demand of the future, more energy resources and energy conversion/harvesting technologies with higher efficiencies are needed. Addressing the problem and providing a radical solution have been attempted in this study. To harvest the renewable energy, among sa variety of solar cells reported, a composite a-Si/CZTS photovoltaic device has not yet been investigated. The calculated parameters for solar cells based on the new array of layers consisting of a-Si/CZTS are reported in this study. The variation of (i) solar cell efficiency as a function of Cu2ZnSnS4 (CZTS) layer thickness, temperature, acceptor, and donor defect concentration; (ii) variation of the open-circuit current density as a function of temperature, open circuit voltage; (iii) variation of open-circuit voltage as a function of the thickness of the CZTS layer has been determined. There has been no reported study on a-Si/CZTS configuration-based solar cell, analysis of the parameters, and study to address the challenges that imped efficiency of the photovoltaic device and the same has been discussed in this work. The value of the SnO2/a-Si/CZTS solar cells obtained from the simulation is 23.9%.

Résumé: The structural, elastic, mechanical, optoelectronic, and thermodynamics properties of InP, InSb, and their mixed ternary alloys, InP1-xSbx, in their zinc blende structure for 0
x
1, are studied. The “full potential linearized augmented plane wave (FP-LAPW) method framed within density functional theory (DFT)" as realized in WIEN2k computational code is employed for all calculations. The results of elastic constants for simulated structures of InP1-xSbx alloys are the first time computed in this study. The results of the elastic constants showed that the InP1-xSbx alloys, for all compositions of x, are brittle and mechanically stable above and beyond showing the strong anisotropic character as well. On the other hand, the obtained results of InP1-xSbx for lattice parameters, bulk modulus, and band gap energy exhibit their nonlinear character. Also, the optical properties are determined at the level of the mBJ scheme for an energy range from 0 to 40eV. However, the “quasi-harmonic Debye model” is used to investigate the thermodynamics properties for example Debye temperature, specific heat, entropy, and their dependence on pressure, and the temperature is also analysed for the mentioned alloys. Our computed results for optical band gap and absorption coefficients expose these alloys as suitable candidate materials for optoelectronics applications in the infrared as well as in the visible region.

Résumé: In this work, we have investigated the crystal growth of the CuGaSe2 chalcopyrite structure compound which is intended for tandem photovoltaic devices. Analyses by X-ray diffraction have shown that the obtained ingots are polycrystalline and have a chalcopyrite structure. The preferential orientation along the plane (112) — very suitable for photovoltaic conversion — was obtained. The lattice parameters a and c were calculated from the X-ray spectra, the ratio c=a was found to be near to 2. The use of an energy dispersive spectrometer (EDS) for the analysis of the chemical composition of the constituents showed that the investigated sample had a stoichiometric ratio Cu/In = 0:99. The morphological analysis performed using a scanning electron microscope (SEM) has shown that the CuGaSe2 compound has a well-crystallized appearance with an average grain size of about 3 m. Characterizations by Hall effect measurements and resistivity have shown that the prepared ingot exhibits a p-type conductivity and low resistivity, of the order of 12.73 cm. The measurement of the photoconductivity of the prepared compound has allowed us to determine the value of the gap at room temperature. The gap was found to be near 1.68 eV. The results obtained within the framework of this study have shown that the prepared CuGaSe2 compound has good crystalline and optoelectronic properties, which makes it one of the ideal compounds to be used as the top cell for a tandem photovoltaic device.

Résumé: This article aims to study MoSe2/ CIGS tandem solar cells employing SCAPS-1D computational package based on ant colony algorithm. The simulation of Monolithic MoSe2/ CIGS tandem solar cells has been implemented successfully by employing the Matlab/Simulink. The power output of the Monolithic MoSe2/ CIGS tandem modules increases by the solar irradiations during the first few days of operation. The J–V characteristic and average daily energy production throughout the year has been calculated. The results show 80.71% FF and 19.29% efficiency of the solar cell. The other parameter for the MoSe2/ CIGS tandem solar cell are Voc = 0.62 V; Jsc = 38.69 mA/cm2.

Résumé: Polycrystalline silicon is widely used in microelectronic and photovoltaic applications. The main problem of[AQ1] this material is the recombination of charge carriers at the grain boundaries which affects the efficiency of the polycrystalline silicon solar cells. In order to improve the crystalline quality and the electrical properties of phosphorus-doped poly-silicon thin films, heat treatments under hydrogen were carried out. This allowed the occupation of the dangling bonds at the grain boundaries and made them inactive, which resulted in improved optoelectronic properties of the treated samples. It has been shown that the effect of hydrogen on the electrical characteristics is more pronounced for low doping concentrations where a 20% improvement of the free carrier concentration was obtained. In addition, the results have shown that the introduction of hydrogen in poly-silicon thin films reduces the density of trap states at the grain boundaries.

Résumé: n the present study, ZnxSn1-xS (x = 0, 0.25, 0.5, 0.75 and 1) thin film samples were deposited by ultrasonic spray pyrolysis technique on glass substrates at 350°C to investigate the effect of variation of Zn concentration (x) on the structural, morphological, optical and electrical properties of ZnxSn1-xS thin films. The films were deposited by varying Zn content in the starting solution. The films deposited were found to be amorphous having root mean square (RMS) roughness ranged from 18.2 to 93.5 nm. The optical characterization by UV-Vis spectroscopy showed that the transmittance and reflectance of all samples are lower than 12.2 % and 10 % respectively. The optical band gap was estimated from the reflectance and transmittance spectra are about 3.86 eV. The carrier mobility is ranged from 113 to 2600 cm2/v.s.

Résumé: The aim of this work is the production and the characterisation of (SnO2: (Mn, F)) thin films with appropriate optoelectronic properties required for application as ohmic contacts in photovoltaic application devices. Transparent conducting Manganese-fluorine co-doped tin oxide (SnO2: (Mn, F)) thin films have been deposited onto preheated glass substrates using the chemical spray pyrolysis (CSP) method. The ([Mn2+]/[Sn4+]) atomic concentration ratio (y) in the spray solution is varied between 0 and 8 at. %. The structural, the opto-electrical and the photoluminescence properties of these thin films have been studied. It is found that the deposited thin films are polycrystalline with a tetragonal crystal structure corresponding to SnO2 phase having a preferred orientation along the (200) plane. Transmission and reflection spectra reveal the presence of interference fringes indicating the thickness uniformity and the surface homogeneity of the deposited samples. Photoluminescence behaviour of Mn-F co-doped SnO2 thin films was also studied. Photoluminescence spectra reveal the presence of the defects like oxygen vacancies in the materials. In addition, The electrical resistivity, volume carrier concentration, surface carrier concentration and electrical mobility were determined from Hall Effect measurements and the following results were obtained: n-type conductivity in all the deposited thin films, a low resistivity of 1.50×10-4 Ω cm, and a high electrical mobility of 45.40 cm2 V-1 s-1 with Mn co-doping concentration equals to 7 at. %. These experimental results show that the electrical properties of these thin films where greatly improved making them suitable as ohmic contacts in photovoltaic applications devices.

Résumé: In this study, structural properties of the zinc-blende (B3) phase and its transition pressure and other important physical properties of GaAs, GaSb compounds, and their mutual alloys for x = 0.25, 0.5 and 0.75 concentration of the Sb are investigated. The computations are carried out using a full-potential (FP) linearised (L) augmented plane wave plus local orbital method (APW + lo) designed within the density functional theory (DFT). The calculations of the structural properties are done at the level of Wu-Cohen generalized gradient approximation (WC-GGA), Perdew-Burke-Ernzerhof approximation (PBE-GGA), as well as Perdew-Wang local density approximation (PW-LDA). Whereas the elastic constants are calculated using WC-GGA. However, to obtain consistent results of the electronic properties, the calculations are carried out by employing Engle-Vosko (GGA) and Tran-Blaha (TB) modified Becke-Johnson (mBJ) potential approach. For each concentration, the pressure-induced phase transition of zinc blende (B3) to rocksalt (B1) structure is investigated. Our band structure calculations show that the alloys are of direct band nature with bandgap energies in a range from 1.559 eV to 0.861 eV with increasing Sb. Furthermore, optical parameters at the level of the mBJ approach are also determined over a range from 0.0 eV to 40.0 eV. From the analysis of our obtained results of enthalpy of mixing, ΔHm, and other properties, it is found that the alloys under investigation are stable over a wide range, and suitable candidates for photovoltaic applications over a wide range of the solar spectrum including visible region.