Titanium dioxide (TiO₂) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO₂ polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO₂ brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO₂ brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO₂ brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO₂ brookite (210) surfaces.

A range of solution-processed organic and hybrid organic−inorganic solar cells, such as dye-sensitized and bulk heterojunction organic solar cells have been intensely developed recently. TiO₂ is widely employed as electron transporting material in nanostructured TiO₂ perovskite-sensitized solar cells and semiconductor in dye-sensitized solar cells. Understanding the optical and electronic mechanisms that govern charge separation, transport and recombination in these devices will enhance their current conversion efficiencies under illumination to sunlight. In this work, density functional theory with Perdew-Burke Ernzerhof (PBE) functional approach was used to explore the optical and electronic properties of three modeled TiO₂ brookite clusters, (TiO₂)_n=5,8,68. The simulated optical absorption spectra for (TiO₂)₅ and (TiO₂)₈ clusters show excitation around 200–400 nm, with (TiO₂)₈ cluster showing higher absorbance than the corresponding (TiO₂)₅ cluster. The density of states and the projected density of states of the clusters were computed using Grid-base Projector Augmented Wave (GPAW) and PBE exchange correlation functional in a bid to further understand their electronic structure. The density of states spectra reveal surface valence and conduction bands separated by a band gap of 1.10, 2.31, and 1.37 eV for (TiO₂)₅, (TiO₂)₈, and (TiO₂)₆₈ clusters, respectively. Adsorption of croconate dyes onto the cluster shifted the absorption peaks to higher wavelengths.

The impact of Na atom deintercalation on olivine NaMnPO₄ was investigated in a first-principle study for prospective use as cathode materials in Na-ion batteries. Within the generalized gradient approximation functional with Hubbard (U) correction, we used the plane-wave pseudopotential approach. The calculated equilibrium lattice constants are within 5% of the experimental data. The difference in equilibrium cell volumes for all deintercalated phases was only 6%, showing that NaMPO₄ is structurally more stable. The predicted voltage window was found to be between 3.997 and 3.848 V. The Na₁MnPO₄ and MnPO₄ structures are likely to be semiconductors, but the Na₀.₇₅MnPO₄, Na₀.₅MnPO₄, and Na₀.₂₅MnPO₄ structures are likely to be metallic. Furthermore, all independent elastic constants for Na_xMPO₄ structures were shown to meet the mechanical stability requirement of the orthorhombic lattice system.

The focus of this study was to assess the solar radiation in locations with limited meteorological data. In 2019, monthly average temperature values that were collected from the South African University Radiometric Network (SAURAN), USAid Venda station in Vuwani, Limpopo, were inputted in the temperature-based empirical model, Hargreaves–Samani ( $H-S$) model to calculate global solar radiation. The modelled monthly average solar radiation values were compared to the ground-based and two satellites data sources. The performance of the model showed strong correlation between all the measurements (observed) solar radiation with R² of 0.83, 0.94, and 0.92 for ground-based, NASA, and CAMS satellites derived data, respectively. It can be inferred that the modelled global radiation has a better error range as compared to both ground-based and satellite-derived observations. The strong correlation validated that the estimated radiation through the $H-S$ model as a reliable input for photovoltaic(PV) power output models for a 255 W panel installed at the study site. Therefore, careful site assessment of weather conditions is necessary for a better assessment of potential P V power output and recommendation of the suitable solar panel. The study has proven that the PV power output can be estimated in areas with limited weather data with known solar panel. The outcomes of this study can be useful for proper design of power generation system of any size in any location.