Anisotropic Lattice Dynamics and Carrier–Phonon Coupling in Sb2Se3 Crystals

Antimony chalcogenides (Sb2X3) have emerged as promising, high-efficiency, and cost-effective photovoltaic materials. We employ femtosecond transient reflectivity (TR) spectroscopy to generate and resolve coherent acoustic phonons (CAPs) propagating along the three principal crystallographic directions of the Sb2Se3 single crystals. Sound velocities extracted from Brillouin oscillation frequencies agree well with the computational results. We quantify the electron–hole deformation potential, which suggests that strongly bound polarons are unlikely in this material. Our measurements demonstrate that highly anisotropic interatomic bonding dictates its elastic response and phonon transport behavior, delivering critical experimental benchmarks to guide the relevant device designs.