Computational study of structural, optical, and mechanical properties of orthorhombic X4Ti3O12 (X = Bi, La, Sc, and Y) for photovoltaic applications

Bismuth titanate is considered as one of the simplest material from the Aurivillius family of perovskites, which has proven to be ideal for the solar energy conversion fundamental for clean and green energy sources. For X4Ti3O12 (X = Bi, La, Sc, and Y) compounds, certain properties including electronic characteristics (band structure, TDOS, and PDOS), optical characteristics (reflectivity, absorption, complex refractive index, complex dielectric function, loss function, and conductivity), and mechanical properties through elastic constants have been investigated. For such complex structure compounds, the choice of ultrasoft pseudopotential plane wave and PBE-GGA approaches have been implemented using the CASTEP tool, which provides a good balance between accuracy and mechanical stability. Among the series, Bi4Ti3O12 is the most rigid compound (Young’s modulus, E = 227.73 GPa) and has demonstrated the highest bandgap of 2.33 eV, whereas 1.40, 1.27, and 0.82 eV are values of bandgaps for La4Ti3O12, Sc4Ti3O12, and Y4Ti3O12 compounds, respectively, making them fall semiconductor in nature. Moreover, high values of absorption coefficient (α = 105 cm−1) and dielectric function (11–13) have been obtained in the visible to mid and far ultraviolet region (1.8–6 eV). On the basis of these properties, it is confirmed that these compounds can be good candidates for photovoltaic applications.