Identification of Excitons and Biexcitons in Sb₂Se₃ under High Photoluminescence Excitation Density

The near‐band‐edge emission of Sb 2 Se 3 microcrystals is studied in detail under high photoluminescence excitation density using a pulsed UV laser (λ = 266 nm, pulse width 0.6 ns). Based on the peak energy positions and the excitation power density and temperature dependencies ( T = 3–110 K) of the photoluminescence spectra, the emission is interpreted as a recombination of two pairs (A and B) of free excitons and biexcitons appearing because of valence band splitting. The magnitude of the valence band splitting due to the crystal field (Δ cr = 20–22 meV) is estimated in the Brillouin zone center. At T = 3 K, the A and B biexciton emission at 1.302 and 1.322 eV, respectively, and the A and B free exciton emission at 1.311 and 1.333 eV, respectively, are observed. The binding energy of A and B biexcitons is 9 and 11 meV, respectively, and the binding energy of A free exciton is 6 meV. The activation energy of thermal quenching for all observed peaks is 20 meV.