New lead-free double perovskites (Rb2GeCl/Br)6; a promising materials for renewable energy applications

The vacancy ordered double perovskites are emerging compounds for optoelectronics, and transport properties. In this article, optical, thermoelectric, mechanical, and thermodynamic properties of Rb2GeCl6 and Rb2GeBr6 are investigated comprehensively. The phonon band structures, and tolerance factor confirm their thermodynamic, and structural stabilities. The direct band gaps 2.60 eV and 1.78 eV are reported at Gamma-symmetry point which ensure the absorption of light from visible to UV regions. The less dispersion of light, and refractive index range 1.5-2 along with broad absorption band in visible to UV regions make them outstanding materials for optoelectronics, Moreover, the transport characteristics are addressed by electrical conductivity, thermal conductivity and Seebeck coefficient, and Figure of merit. The room temperature ZT values 0.78, and 0.74 also ensure their importance for thermoelectric applications. The mechanical properties confirm their ductile, ionic, and anisotropic nature. The high Debye, and melting temperatures increases their heating resistant capacity and stability.

Automated summary

The article comprehensively investigates the optical, thermoelectric, mechanical, and thermodynamic properties of Rb2GeCl6 and Rb2GeBr6 vacancy ordered double perovskites. The materials exhibit promising characteristics for optoelectronics and thermoelectric applications, with direct band gaps ensuring light absorption from visible to UV regions and high ZT values indicating their importance in thermoelectricity. Additionally, their mechanical properties confirm their ductile, ionic, and anisotropic nature, with high Debye and melting temperatures enhancing their resistance to heating.