Structural, Optoelectronic, Elastic, Thermodynamic, and Photovoltaic Properties of Novel Sr 3 NX 3 (X = F, Cl, Br, and I) Compounds: A First-Principles FP-LAPW Study

Abstract

Lead-free inorganic halide compounds have recently been considered excellent materials for use in photovoltaic/optoelectronic applications because of their environmentally friendly nature. In present study, structural, optoelectronic, mechanical, thermodynamical and photovoltaic properties of cubic Sr 3 NX 3 (X = F, Cl, Br, I) compounds have been studied using the all-electron FP-LAPW+lo method within the density functional theory framework. As X changes from fluorine to iodine, lattice constant increases from 5.191 Å to 6.354 Å, but bulk modulus decreases from 57.621 GPa to 28.420 GPa. These results show that lattices become softer as the halogens change from fluorine to iodine. The direct band gaps reduce from 3.454 eV (Sr 3 NF 3 ) to 1.172 eV (Sr 3 NI 3 ). All the studied compounds are mechanically stable, and they have strong absorption of visible light (∼10 5 cm −1 ). Debye temperatures range between 423.79 K and 234.24 K, while pressure increases lattice stability. SLME values of 2.17%, 26.27%, 35.73%, and 51.60% identify Sr 3 NBr 3 and Sr 3 NI 3 as promising candidates for high-efficiency photovoltaic applications.