Comprehensive first-principles investigation of strain-induced semiconductor-to-metal transition in FrSnA₃(A=Cl, Br, I) halide perovskite

Currently, solar cells utilizing organic–inorganic halide perovskite materials stand out as one of the most interesting subjects in the field of renewable energies. This paper explored the effect of biaxial compressive and tensile strain on the structure, optoelectronic features, and mechanical properties of the Fr-based perovskite FrSnA 3 (A[Formula: see text]Cl, Br, I) through first-principles density-functional theory (FP-DFT). The calculated tolerance factors for FrSnCl 3 , FrSnBr 3 , and FrSnI 3 are 0.85, 0.85, and 0.84, respectively, confirming the cubic crystal structure of these compounds. Furthermore, the structural stability of these compounds is affirmed by their alignment with the Birch–Murnaghan fit curve during optimization. All three compounds, FrSnCl 3 , FrSnBr 3 , and FrSnI 3 , exhibit semiconductor behavior with direct band gaps of 1.05, 0.66, and 0.44[Formula: see text]eV, respectively. The investigation shows that applying tensile strain leads to an increase in the band gap, whereas compressive strain results in its reduction across these materials. The evaluation of elastic properties confirms that these structures are mechanically stable, ductile, and anisotropic. Moreover, the findings of optical properties indicate that because of the dimensional expansion, the optical absorption edges of FrSnA 3 (A[Formula: see text]Cl, Br, I) have a blue shift and move toward higher energies. In contrast, a reduction in lattice dimensions induces a red shift, shifting the onset of optical absorption to lower energy regions. The evaluated optical responses indicate that the examined materials hold promise for use in optoelectronic devices with tunable performance under applied strain.