Strong optical absorption in cubic RaMS₃ chalcogenide perovskites for optoelectronic applications: a first-principles...

Chalcogenide perovskites exhibit tunable electronic and optical properties arising from chalcogen-based bonding and versatile cation chemistry. While substantial progress has been achieved for orthorhombic chalcogenide perovskites, the cubic phase remains comparatively underexplored, particularly for systems incorporating transition-metal elements and large A-site cations. Here, we theoretically investigate a new family of cubic chalcogenide perovskites, RaMS₃ (M = Ti, Zr, Hf), using first-principles calculations to examine their structural, electronic, optical, and mechanical properties. Hybrid functional results reveal that all three compounds are indirect-band-gap semiconductors with band gaps ranging from 0.47 to 1.54 eV, covering the infrared to visible regions. Density-of-states analysis shows that the valence bands are dominated by S-p states, while the conduction bands primarily originate from transition-metal d states, highlighting the importance of the corner-sharing MS₆ octahedral framework. The optical response demonstrates strong visible-light absorption for RaZrS₃ and RaHfS₃, with spectroscopic limited maximum efficiencies of approximately 22%, 27%, and 30% for RaTiS₃, RaZrS₃, and RaHfS₃, respectively. Phonon calculations show that cubic RaZrS₃ and RaHfS₃ are dynamically stable at 0 K, whereas RaTiS₃ exhibits imaginary phonon modes within the harmonic approximation, indicating the instability of the ideal cubic phase at zero temperature. Finite-temperature anharmonic phonon calculations based on the self-consistent phonon method demonstrate that these soft modes are renormalized and the cubic phase becomes dynamically stable at 300 K. Overall, these results provide insight into the electronic and optical behavior of cubic chalcogenide perovskites containing large A-site cations and offer guidance for the design of related materials with potential relevance for optoelectronic studies.