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.
First-principle calculations were used to investigate the structural, optoelectronic, elastic and thermodynamic properties of Br-doped CsPbI3 perovskite material using GGA-PBE, SCAN, and LDA functionals. The computed lattice parameters are consistent with the experimental and theoretical calculations, reported in the literature. The band structure along with the electronic density of states indicated that CsPbI3-xBrx (x = 0, 1, 2, 3) materials are semiconductors with direct band gaps, as projected using the three functionals. The energy band gap of CsPbI3 was tuned by replacing I ions with Br ions, resulting in CsPbI2Br, CsPbBr2I, and CsPbBr3 materials. These perovskite materials were found to be mechanically stable, ductile in nature and elastically anisotropic. The results of optical parameters such as absorption coefficients, refractive index, optical conductivity, optical reflectivity, electron energy loss, and extinction coefficients were calculated and analysed. The thermodynamic parameters including heat capacity, and Debye temperature were calculated. The direct band gap and energy-dependent optical parameters especially the absorption coefficient in the infrared and visible region of these perovskites’ materials suggest that they might be candidates for potential use in photovoltaic solar cells and optoelectronic applications.
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