Study of phase Stability, Optical, and thermoelectric properties of antiperovskites X₃GeO (X=Ca, Sr, Ba) for solar cells and energy harvesting

Perovskites and their inverse derivatives are emerging aspirants for solar cells and energy harvesting applications. Herein, we have comprehensively addressed the phase stability, optical, and transport characteristics of X₃GeO (X=Ca, Sr, Ba) antiperovskites by first-principles analysis. The studied compounds have an orthorhombic crystal structure with a space group (1-P1). The phonon spectra have been computed to assess the dynamic stability. The electronic band structures demonstrate that perovskites have narrow band gaps, while the antiperovskites are narrow band gap semiconductors. The calculated values of band gaps for antiperovskites are 0.38, 0.63, and 0.70 eV, respectively, suggesting optimal absorption in infrared to visible regions. Light energy's dispersion and absorption are calculated by a complex dielectric function, refractive index, and absorption coefficient in the energy range 0 to 5 eV. The Seebeck coefficient, electrical & thermal conductivities, and power factor assess thermoelectric performance at increasing temperatures and carrier concentration. The findings convey a theoretical foundation for future experimental investigations of these antiperovskites and suggest their effectiveness for optoelectronic, and thermoelectric applications to harvest green energy.