Among the existing commercial cathodes, Ni-rich NCM are the most promising candidates for next-generation LIBs because of their high energy density, relatively good rate capability, and reasonable cycling performance.

Photocatalysis is a more proficient technique that involves the breakdown or decomposition of different organic contaminants, various dyes, and harmful viruses and fungi using UV or visible light solar spectrum.

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In this work, using the Quantum ESPRESSO package, density functional theory was used to study the effects of different metal dopants on the structural and electronic properties of tetragonal α-PbO. Tetragonal α-PbO has attracted attention due to its application in various optoelectronic devices. However, in order to apply it in these technologies suitably, its properties have to be improved since it has low electronic conductivity. In this study, nine different metals from alkali metals, p-block metals, and 3d-transition metals have been used as dopants to investigate its electronic properties. Moreover, the performance of four pseudopotentials was tested. Via the partial density of state and band structure calculations, an indirect bandgap was found for pristine α-PbO. The generalized gradient approximation of the Perdew–Burke–Ernzerhof exchange correlation with ultrasoft pseudopotential gives 1.75 eV for pristine α-PbO, which decreased during the incorporation of different metal dopants. Depending on the position of the Fermi level and impurity energy level in metal doping, the n- or p-type conductivity has been identified. The calculated partial density of states shows the contribution of orbital states of dopants to the partial density of states. The valence band maximum is mainly made of O-2p states whereas the conduction band minimum is dominated by Pb-6p states in undoped α-PbO. The calculated lattice constants were a = b = 3.997 Å and c = 5.220 Å, which are in best agreement with the experimental values. The computational study verified that doping various metals had a significant effect on the structural and electronic properties of α-PbO.

In recent days, metallic oxide semiconductor nanoparticles have drawn attention to the photocatalytic degradation of organic pollutants. In the present work, undoped and different metals (Sn, Co, Cu, Ni, and Li)-doped of α-PbO nanoparticles were successfully synthesized by a facile chemical precipitations method. The obtained nanoparticles were further studied by using different characterization techniques. The XRD results confirmed that the prepared nanoparticles were a tetragonal, α-PbO phase crystal structure without mixing other PbO phases. The obtained optical band gaps from UV-Vis DRS analysis were 2.03 eV, 2.68 eV, 1.61 eV, 1.78 eV, 1.67 eV, and 2.00 eV for pristine α-PbO, Sn, Co, Cu, Ni, and Li doped α-PbO respectively. From the PL emission, the lowest PL intensity of the doped samples indicated the low recombination of the electron-hole pairs that improved the photocatalytic performance of pristine α-PbO. SEM and EDX were used to analyze the surface morphology and composition of the synthesized nanoparticles, respectively. The photocatalytic activities of the prepared nanoparticles were assessed through the degradation of the Methylene Blue (MB) dye under visible light irradiation. The UV-Visible spectrophotometer analysis showed that the MB dye concentration decreased as the irradiation time varied from 20 to 100 min. The results showed that within 100 minutes, the Sn-doped α-PbO nanoparticles possessed the maximum degradation efficiency compared to other metal-doped α-PbO nanoparticles, with 100 % MB dye degradation compared to 94.76 % by pristine α-PbO. This was due to the increased visible light harvesting, which aided in the photocatalytic degradation of MB dye.

In this research, the ranges of the localized states in which the recombination and the trapping rates of free carriers dominate the entire transition rates of free carriers in the bandgap of the p-type semiconductor are described. Applying the Shockley–Read–Hall model to a p-type material under a low injection level, the expressions for the recombination rates, the trapping rates, and the excess carrier lifetimes (recombination and trapping) were described as functions of the localized state energies. Next, the very important quantities called the excess carriers’ trapping ratios were described as functions of the localized state energies. Variations of the magnitudes of the excess carriers’ trapping ratios with the localized state energies enable us to categorize the localized states in the bandgap as the recombination, the trapping, the acceptor, and the donor levels. Effects of the majority and the minority carriers’ trapping on the excess carrier lifetimes are also evaluated at different localized energy levels. The obtained results reveal that only excess minority trapping affects the excess carrier lifetimes, and excess majority carrier trapping has no effect.

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In this paper, first, the theoretical description of the effects of the dopant densities and the activation energies on the ionization densities, the chemical potentials corresponding to each dopant levels, the majority carrier densities and the Fermi-energy levels in one-acceptor-level system, highly compensated system and two-acceptor-level system are described in detail. Upon fitting the theoretical to the experimental results obtained by the temperature-dependent Hall effect measurements for three samples of un-doped GaSb, the dopant densities and the activation energies for a system with different dopants are investigated. The obtained results revealed that the dopant activation energy has less (no) effect on the Fermi-energy level and the majority carrier density in the highest temperature regimes. The doping density has also less (no) effect on the Fermienergy level in the lowest temperature regimes. Finally, fitting of the theoretical to the experimental Hall effect measurements results confirmed the presence of three acceptor and one donor levels dominating the majority carrier densities at different temperature regions in all the samples of un-doped GaSb semiconductor.