Revealing structural, elastic, optoelectronic and thermoelectric properties of lead-free Ba₂XTiO₆ (X = Hf, Ce, Te) double perovskite for solar cells applications

The non-toxic nature, low cost, and excellent optical properties make oxide-based perovskites potential candidates for solar cell applications. The full potential linearized augmented plane wave approach is applied to explore the structural, electronic, optical, and thermoelectric properties of Ba₂XTiO₆ (X = Hf, Ce, and Te) for solar cell applications. As demonstrated by an elastic study, Ba₂HfTiO₆ is brittle, while Ba₂CeTiO₆ and Ba₂TeTiO₆ are ductile. The anisotropic values of Ba₂HfTiO₆, Ba₂CeTiO₆ and Ba₂TeTiO₆ are 1.14, 0.67 and 0.80 respectively. The electronic bandgap values of Ba₂HfTiO₆, Ba₂CeTiO₆, and Ba₂TeTiO₆ are computed as 3.44 eV, 2.96 eV, and 1.26 eV using the Tran-Blaha-modified Becke-Johnson approach. Moreover, the bandgap of Ba₂TeTiO₆ is compatible for solar cell applications. Optical investigation demonstrates that Ba₂TeTiO₆ shows maximum absorption in visible light among the studied perovskites. Lastly, the transport properties exhibit figure of merit values of 0.79, 0.75 and 0.85 for Ba₂HfTiO₆, Ba₂CeTiO₆, and Ba₂TeTiO₆ respectively. Consequently, with the bandgap falling in the visible region and high figure of merit among the studied perovskites, Ba₂TeTiO₆ emerges as the most suitable candidate for solar cell applications based on its electronic, optical, and thermoelectric properties.