Unveiling the structural and functional properties of Ba2XGe2O7 melilite phases for advanced photovoltaic devices

In this study, mechanical, optical, structural, elastic, and electronic properties of melilite material group members Ba2XGe2O7 (X = Mg, Ca, Zn, and Sr) are investigated by utilizing the GGA (Generalized gradient approximation) approach and the PBE (Perdewe–Burke–Ernzerhof) approach in DFT technique. In this approach, the estimated band gaps for Ba2MgGe2O7 (3.487 eV), Ba2CaGe2O7 (3.475 eV), Ba2ZnGe2O7 (2.954 eV), and Ba2SrGe2O7 (2.780 eV) by GGA-PBE approach and the obtained bandgap values for Ba2MgGe2O7 (3.381 eV), Ba2CaGe2O7 (3.313 eV), Ba2ZnGe2O7 (2.931 eV), and Ba2SrGe2O7 (2.724 eV), achieved by using HSE06, reveal that they are semiconductors in nature and good fit for flexible optoelectronic devices. Furthermore, the study of powder XRD by reflex tool demonstrates that compounds possess unique diffraction peaks, and the characteristic peak is reported at 28.3°. The optical characteristics, such as optical conductivity (4.3 fs−1), dielectric function (4–5), absorption coefficient (105 cm−1), and refractive index (2–2.5), have shown high values in the visible and ultraviolet regions. Anisotropic behavior in mechanical characteristics has been observed in the XY, YZ, and XZ planes. Both the Poisson and Pugh ratios for the compounds indicate the ductile nature of the compounds. The mechanical properties also confirm their ductility and suggest that they are stable enough for flexible photovoltaic applications. This study provides important insights about these compounds to confirm their potential utilization for next-generation solar cell technologies.