Strain-Driven Optical, Electronic, and Mechanical Properties of Inorganic Halide Perovskite CsGeBr ₃

Of late, inorganic perovskite material, especially the lead-free CsGeBr 3, has gained considerable interest in the green photovoltaic industry due to its outstanding optoelectronic, thermal, and elastic properties. This work systematically investigated the strain-driven optical, electronic, and mechanical properties of CsGeBr 3 through the first-principles density functional theory. The unstrained planar CsGeBr 3 compound demonstrates a direct bandgap of 0.686 at its R-point. However, incorporating external biaxial tensile (compressive) strain can be tuned the bandgap lowering (increasing) to this perovskite. Moreover, due to the increase of tensile (compressive) strain, a red-shift (blue-shift) behavior of the absorption-coefficient and dielectric function is found in the photon energy spectrum. Strain-induced mechanical properties also reveal that CsGeBr 3 perovskites are mechanically stable and highly…