First-Principles Investigation of the Structural, Electronic, Mechanical, and Optical Properties of A₃NBr₃ (A = Ca, Sr, and Ba)

Numerous compounds from the A<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>BX<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> perovskite family function as non-toxic halide perovskites, fulfilling the essential requirements for commercializing optoelectronic devices. This study thoroughly examines the structural, electronic, mechanical, and optical traits exhibited by A<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>NBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> perovskites (where A = Ca, Sr, and Ba) through the application of density functional theory (DFT). The alternation characterized by the A site cation from Ca to Sr to Ba increases lattice constant and unit cell volume while preserving thermodynamic stability. Electronic band structure investigations unveil direct bandgaps for the investigated compounds, with a linear decrease in bandgap while changing the A site cation from Ca to Sr to Ba, rendering them beneficial for optoelectronic applications. The mechanical properties reveal that Ca<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>NBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and Sr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>NBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> are brittle, whereas Ba<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>NBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> exhibits ductility, expanding its potential application in flexible device technologies. The change in A site cation from Ca to Sr to Ba exhibits better optical properties, encompassing favorable dielectric constants and higher absorption coefficients, making them more appropriate candidates for both photovoltaic and other optoelectronic applications. This comprehensive study elucidates the basic characteristics of A<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>NBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> perovskites, opening up new opportunities for their integration into next-generation electronic and optoelectronic technologies.