Background. Air pollution has become a major problem around the world and is increasingly an issue in Togo due to increased vehicular traffic. Gaseous pollutants are released by engines and are ver...

An experiment to study an exotic atom with infrared spectroscopy will measure a fundamental parameter related to the spatial dimensions of a proton.

A steplike density of states is the hallmark of a two-dimensional electron gas. Here, scanning tunneling spectroscopy is used to investigate this property in the differential conductance of an $\mathrm{I}{\mathrm{n}}_{0.53}\mathrm{G}{\mathrm{a}}_{0.47}\mathrm{As}$ quantum well grown on $p$-type doped InP(001). We show that the appearance of a steplike function in the conduction band strongly depends on both the hole concentration in the quantum well and the current injected into the quantized states. Based on four-point probe transport measurements and tunneling-induced light-emission spectroscopy, we discuss the physical mechanisms at the origin of the current and unveil the significant contribution of midgap surface states in the relaxation of the tunneling electrons. These surface states, via pinning of the Fermi level, also affect the potential landscape across the quantum well, as demonstrated by tight-binding calculations of the quantum well electronic structure.

This study presents the influence of pH control agents and pH value on the physical properties of ZnO thin films obtained by chemical bath deposition. ZnO thin films were synthesized on glass substrates using precursor solutions of different pHs prepared from two bases: sodium hydroxide (NaOH) and ammonia (NH₃). The effect of pH values on the morphological, structural, and optical properties of ZnO thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV–Visible spectroscopy. XRD results showed that all the synthesized ZnO thin films are polycrystalline and crystallize in a hexagonal wurtzite structure. The crystallite size, calculated using the Debye–Scherrer formula, varied from 10.50 nm to 11.69 nm for ZnO thin films obtained with NH₃ and from 20.79 nm to 27.76 nm for those obtained with NaOH. FTIR analysis confirmed the presence of functional groups. SEM images indicated that not only the base but also the pH affects the morphology of the films, giving rise to different granular shapes. Overall, the ZnO thin films obtained with NaOH looked more mesoporous compared to those obtained with NH₃. Optical characterization results showed that whatever the base used, the pH of the precursor solution affected the ZnO thin film transmittance. Films synthesized with NH₃ exhibited the best transmittance (80%) at pH 8.5, while the best transmittance (81%) of films synthesized with NaOH was obtained at pH 8 in the visible region. Based on optical and morphological properties, ZnO films obtained from NH₃ at pH 8.5 are found to be more suitable as photoanodes in dye-sensitized solar cells.

The high conversion efficiency of solar cells can make them more competitive in cost compared to conventional energy sources. Therefore, enhancing photovoltaic cell efficiency remains a critical challenge for researchers and manufacturers. Shockley-Queisser single junction photovoltaic cells are limited to 33.7%, and multi-junction solar cells are the most promising technologies that have achieved remarkable efficiencies exceeding 46%. Modeling and simulation are essential to optimize semiconductor devices and reduce their development time and cost. This study investigates the performance improvement of novel InGaP/InGaAs/Ge triple-junction solar cells by integrating III-V semiconductors. The design includes Tungsten disulfide as an electron transport layer, reduced graphene oxide as a hole transport layer, and intrinsic InGaAs layers to improve efficiency in decreasing the number of InGaP, InGaAs, and Ge layers to reduce manufacturing costs. SCAPS 1D software was used to simulate under a solar irradiance of 1000 Wm-2 and an air mass of AM1.5G spectrum at 25°C. In addition, a commercial InGaP/InGaAs/Ge solar cell and a mini-solar panel were also simulated, and the obtained current-voltage characteristics were compared with experimental data. A strong correlation was observed between the simulated data and the experimental measurements, confirming the proposed solar cell design's potential, accuracy, and reliability. The new structure produced an impressive power conversion efficiency of 49.83%. The findings suggest a route to manufacturing new multi-junction photovoltaic cells with high efficiency and lower cost.