Rare-earth chalcogenide perovskites: A promising class of materials for optoelectronic applications

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Rare-earth chalcogenide perovskites have attracted significant attention for optoelectronic applications due to their nontoxic composition, robust phase stability, and excellent optoelectronic properties. However, their excitonic and polaronic properties remain largely unexplored due to the high computational cost of accurate theoretical treatments. In this work, we present a comprehensive first-principles investigation of excitonic dynamics and polaronic effects in a series of III-III rare-earth chalcogenide perovskites ABX₃ (A = Y, La; B = Sc, Y; X = S, Se), along with their structural stability and optoelectronic properties, using state-of-the-art density functional theory in conjunction with many-body perturbation theory within the G₀W₀ and Bethe-Salpeter equation (BSE) frameworks. All investigated compounds satisfy the dynamical and mechanical stability criteria. They exhibit quasiparticle band gaps in the range of 2.75-4.47 eV, and the BSE calculations reveal strong optical absorption spanning the visible to ultraviolet regions. The computed excitonic properties indicate intermediate-to-large exciton binding energies (0.148-0.517 eV), moderately localized excitons, and strong electron-hole wavefunction overlap, indicative of favorable radiative recombination characteristics and enhanced light-matter interaction. Furthermore, analysis based on the Fröhlich model demonstrates intermediate-to-strong carrier-phonon coupling, with electron-phonon interactions generally stronger than hole-phonon interactions. Overall, rare-earth chalcogenide perovskites ABX₃ exhibit a compelling combination of structural stability, tunable optoelectronic properties, pronounced excitonic effects, and favorable polaronic transport, positioning them as promising lead-free materials for next-generation optoelectronic devices, including light-emitting devices and photodetectors.