Simulation and analysis of solar cells based on the heterojunction of zinc oxide doped with aluminum (AZO) and cadmium telluride (CdTe) with the structure (Al/AZO/CdTe/NiO/Ni) using the Simulator of the capacitance of solar cells - 1 dimension (SCAPS-1D) has been presented in this paper. AZO is used as a window layer and Nickel oxide (NiO) has been introduced as a hole transport layer (HTL). Through the software, the effect of thickness, absorber (CdTe), and window (AZO) layers carrier concentration, operating temperature, and resistances (series and shunt) have been studied. Simulation results show that the solar cell performance can be greatly improved by adjusting the layer's thickness and carrier concentration, obtaining optimal values of 10 nm and 10 18 c m - 3 for the AZO layer, while for the CdTe layer they were 2 μm and 10 15 c m - 3 . The optimum series and shunt resistances are in the range of 1-3 Ω c m 2 and 1800-2200 Ω c m 2 respectively. A maximum power conversion efficiency (PCE) of 14.2% is achieved with an open circuit voltage (Voc) of 0.74 V, short circuit current density (Jsc) of 26.15 m A / c m 2 and a fill factor (FF) of 72.83%, this shows AZO potential to be considered as an interesting material to replace CdS window layer.

We studied the influences of the thickness of the porous silicon layer and the conductivity type on the porous silicon sensors response when exposed to ethanol vapor. The response was determined at room temperature (27 ${}^{\circ }$C) in darkness using a horizontal aluminum electrode pattern. The results indicated that the intensity of the response can be directly or inversely proportional to the thickness of the porous layer depending on the conductivity type of the semiconductor material. The response of the porous sensors was similar to the metal oxide sensors. The results can be used to appropriately select the conductivity of semiconductor materials and the thickness of the porous layer for the target gas.

In this paper, a solar cell based on ${\mathrm{W}\mathrm{O}}_3$/CdTe heterojunction was analyzed and optimized, for which the following structure of the Al/AZO/${\mathrm{W}\mathrm{O}}_3$/CdTe/NiO/Ni device was proposed, which was numerically simulated by the SCAPS 1-D software. Using the software, the effect of the thickness and carrier concentration of the absorber layer (CdTe) and the window layer (${\mathrm{W}\mathrm{O}}_3$) was analyzed, and the optimal value of these parameters was found to be 2 µm and ${10}^{15}{\mathrm{c}\mathrm{m}}^{-3}$ for the CdTe layer and 10 nm and ${10}^{19}{\mathrm{c}\mathrm{m}}^{-3}$ for the ${\mathrm{W}\mathrm{O}}_3$ layer, respectively. The influence of the defect density of the ${\mathrm{W}\mathrm{O}}_3$/CdTe interface on the performance of the proposed cell was also analyzed, simulating from ${10}^{10}$ to ${10}^{16}$ ${\mathrm{c}\mathrm{m}}^{-2}$, obtaining better device performance at lower interface defect density. Another parameter analyzed was the operating temperature on the photovoltaic performance of the device, observing that the solar cell has a better performance at lower temperatures. Finally, a maximum optimized PCE of 19.87% is obtained with a V_oc = 0.85 V, J_sc = 28.45 $\mathrm{m}\mathrm{A}/{\mathrm{c}\mathrm{m}}^2$, and FF = 82.03%, which makes the ${\mathrm{W}\mathrm{O}}_3$/CdTe heterojunction an interesting alternative for the development of CdTe-based solar cells.

In this work, the application of RF power in stepped mode during the growth process of CdTe films deposited on glass substrates at room temperature and their structural, morphological, and optical properties were studied. The working pressure and deposition time during deposition were 10 mTorr and 120 min, respectively, meanwhile the RF power was gradually varied from 30 W to 40 W. For comparison and reference, CdTe films with 30 W and 40 W (fixed power values) were also deposited, which resulted amorphous. The x-ray diffraction results of the films prepared with stepped RF power were polycrystalline with cubic structure and (111) as preferential orientation. The crystallite size of films changes from 16.6 to 29.2 nm as the rate of the stepped RF power increases. Raman spectra show that intensity of peaks located at 123, 140 and 164 cm-1 increase with the increased rate of stepped RF power, as well as the rms-roughness and grain size values increase from 0.8 nm to 1.6 nm and from 62.8 nm to 92.1 nm, respectively. The UV-Vis spectra show that the bandgap energy of the deposited CdTe films changes from 1.47 to 1.54 eV with the increased rate of stepped RF power. The obtained bandgap energy values of the CdTe films are adequate to be used as absorber material for photovoltaic applications into the ZnO/CdTe and CdS/CdTe solar cells.

The effect of the deposit temperature of zinc oxide (ZnO) doped with nickel (Ni) by hot filament chemical vapor deposition (HFCVD) technique is reported in this work. The technique allows depositing ZnO:Ni in short intervals (1 min). A deposit of undoped ZnO is used as a reference sample. The reference sample was deposited at 500 °C. The ZnO:Ni samples were deposited at 500 °C, 400 °C, 350 °C, and 300 °C. The samples were studied using structural, morphological, and optical characterization techniques. The Ni incorporation to the ZnO lattice was verified by the shift of the X-ray diffraction peaks, the Raman peaks, the band gap, and the photoluminescence measurements. It was found that the deposit temperature affects the structural, morphological, and optical properties of the ZnO:Ni samples too. The structure of the ZnO:Ni samples corresponds to the hexagonal structure. Different microstructures shapes such as spheres, sea urchins, and agglomerate were found in samples; their change is attributed to the deposit temperature variation. The intensity of the photoluminescence of the ZnO:Ni improves concerning the ZnO due to the Ni incorporation, but it decreases as the deposit temperature decreases.

Tantalum-doped ZnO structures (ZnO:Ta) were synthesized, and some of their characteristics were studied. ZnO material was deposited on silicon substrates by using a hot filament chemical vapor deposition (HFCVD) reactor. The raw materials were a pellet made of a mixture of ZnO and Ta₂O₅ powders, and molecular hydrogen was used as a reactant gas. The percentage of tantalum varied from 0 to 500 mg by varying the percentages of tantalum oxide in the mixture of the pellet source, by holding a fixed amount of 500 mg of ZnO in all experiments. X-ray diffractograms confirmed the presence of zinc oxide in the wurtzite phase, and metallic zinc with a hexagonal structure, and no other phase was detected. Displacements to lower angles of reflection peaks, compared with those from samples without doping, were interpreted as the inclusion of the Ta atoms in the matrix of the ZnO. This fact was confirmed by energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) measurements. From scanning electron microscopy (SEM) images from undoped samples, mostly micro-sized semi-spherical structures were seen, while doped samples displayed a trend to grow as nanocrystalline rods. The presence of tantalum during the synthesis affected the growth direction. Green photoluminescence was observed by the naked eye when Ta-doped samples were illuminated by ultraviolet radiation and confirmed by photoluminescence (PL) spectra. The PL intensity on the Ta-doped ZnO increased from those undoped samples up to eight times.