Decoding optoelectronic behavior in X$_3$BI$_3$ antiperovskite derivatives through many-body perturbation theory

TL;DR

The paper addresses the need for stable, lead-free optoelectronic materials by studying X$_{3}$BI$_{3}$ halide antiperovskite derivatives with first-principles many-body perturbation theory. Using DFT, HSE06, DFPT, and GW-BSE, it maps structural stability, electronic structure, dielectric screening, excitonic effects, and polaron dynamics across Ca/Sr and P/As/Sb/Bi with I, identifying five compositions dynamically stable and exhibiting direct bandgaps in the visible, moderate exciton binding, and sizeable polaron mobilities. The work shows electronic screening dominates excitonic behavior, with small phonon corrections, and reveals intermediate Fröhlich coupling ($\alpha$ = 1.91–4.83) yielding large polarons and mobilities up to $37.19$ cm$^{2}$V$^{-1}$s$^{-1}$. Together, these findings position X$_{3}$BI$_{3}$ as promising, stable, lead-free candidates for efficient photovoltaics and light-emitting devices, guiding experimental exploration.

Abstract

Antiperovskite derivatives have emerged as promising candidates for optoelectronic applications. However, due to the significant computational cost, their excitonic and polaronic properties remain underexplored despite being critical for optoelectronic performance. Here, we present the structural, electronic, optical, excitonic, and polaronic properties of a series of antiperovskite derivatives with the chemical formula X$_{3}$BI$_{3}$ (X = Ca, Sr; B = P, As, Sb, Bi) using state-of-the-art first-principles calculations. All the compounds exhibit direct bandgaps with G$_{0}$W$_{0}$@PBE bandgap ranging from 2.42 to 3.02 eV, optimal for efficient light absorption with minimal energy loss. Exciton binding energies (0.258-0.318 eV) indicate moderate Coulomb attraction, favoring exciton dissociation. Employing the Feynman polaron model, we established the polaronic properties, where weak to intermediate carrier-phonon coupling was observed, with polaron mobilities reaching values up to 37.19 cm$^{2}$V$^{-1}$s$^{-1}$. These properties establish X$_{3}$BI$_{3}$ materials as viable candidates for next-generation optoelectronic devices.

Figures (4)

• Figure 1: Schematic illustration of the transformation from antiperovskite X$_{3}$BA (left) to its derivative X$_{3}$BA$_{3}$ (right) structure. In X$_{3}$BA, the single A atom at (0, 0, 0) is replaced in X$_{3}$BA$_{3}$ by three A atoms located at (0.5, 0, 0), (0, 0.5, 0), and (0, 0, 0.5). The color scheme in the chemical formulas corresponds to the atom colors in the structures: green- X-site atoms (Ca/Sr), blue- B-site atoms (P/As/Sb/Bi), purple- “ A” atom in X$_{3}$BA, and cyan- three “ A” atoms in X$_{3}$BA$_{3}$. In the present study, we specifically investigate the X$_{3}$BA$_{3}$ systems with X = Ca, Sr; B = P, As, Sb, Bi; and A = I.
• Figure 2: Phonon dispersion curves of the a) Ca$_{3}$PI$_{3}$, b) Ca$_{3}$AsI$_{3}$, c) Ca$_{3}$SbI$_{3}$, d) Ca$_{3}$BiI$_{3}$, e) Sr$_{3}$PI$_{3}$, f) Sr$_{3}$AsI$_{3}$, g) Sr$_{3}$SbI$_{3}$, and h) Sr$_{3}$BiI$_{3}$ antiperovskite derivative, respectively.
• Figure 3: Electronic band structures of a) Ca$_{3}$PI$_{3}$, b) Ca$_{3}$AsI$_{3}$, c) Ca$_{3}$SbI$_{3}$, d) Ca$_{3}$BiI$_{3}$, e) Sr$_{3}$PI$_{3}$, f) Sr$_{3}$AsI$_{3}$, g) Sr$_{3}$SbI$_{3}$, and h) Sr$_{3}$BiI$_{3}$ antiperovskite derivative, respectively, calculated using the G$_{0}$W$_{0}$@PBE method. The fermi level is set to be zero and marked by the dashed line.
• Figure 4: Real [Re ($\varepsilon$)] and imaginary [Im ($\varepsilon$)] part of the dielectric function of a) Ca$_{3}$PI$_{3}$, b) Ca$_{3}$AsI$_{3}$, c) Ca$_{3}$SbI$_{3}$, d) Ca$_{3}$BiI$_{3}$, e) Sr$_{3}$PI$_{3}$, f) Sr$_{3}$AsI$_{3}$, g) Sr$_{3}$SbI$_{3}$, and h) Sr$_{3}$BiI$_{3}$ antiperovskite derivative, respectively, obtained using the BSE@G$_{0}$W$_{0}$@PBE method.