📝 SummarXiv

Abstract

Inorganic antiperovskite nitrides have recently emerged as promising materials for photovoltaic applications, yet their nonradiative recombination dynamics remain largely unexplored. Here, we examine the influence of X-site cation substitution on the nonradiative electron-hole recombination in $\mathrm{X_{3}NSb}$ ($X = \mathrm{Ca}, \mathrm{Sr}, \mathrm{Ba}$). Ca- and Sr-based compounds adopt a cubic phase, whereas Ba stabilizes in a hexagonal structure, introducing pronounced symmetry-driven effects. Substituting Ca with Sr narrows the band gap, suppresses octahedral and band-edge fluctuations, reduces nonadiabatic (NA) coupling by $\sim 54\%$, and extends carrier lifetimes by a factor of $2.5$. In contrast, Ba substitution increases lattice distortion, widens the band gap, and enhances NA coupling beyond that of $\mathrm{Sr_{3}NSb}$, thereby accelerating recombination through stronger lattice fluctuations. The resulting band gap fluctuations in $\mathrm{Ba_{3}NSb}$ also shorten decoherence times, following the trend $\mathrm{Ba_{3}NSb} < \mathrm{Ca_{3}NSb} < \mathrm{Sr_{3}NSb}$. Our results demonstrate how the interplay between band gap, NA coupling, and decoherence time governs recombination lifetimes, with $\mathrm{Sr_{3}NSb}$ exhibiting the longest lifetime. These findings highlight the coupled influence of cation chemistry and crystal symmetry in tailoring carrier dynamics for high-performance antiperovskite-based optoelectronics materials.