Study of defects in chlorine-doped Sb2Se3 single crystals by photoluminescence spectroscopy

Chlorine doping has been shown to significantly affect the electrical and optical properties of antimony selenide (Sb₂Se₃), yet its impact on defect-related radiative recombination remains poorly understood. In this study, we investigated the influence of Cl doping on the defect structure of Sb₂Se₃ single crystals using temperature- and excitation power-dependent photoluminescence (PL) spectroscopy, in direct comparison with an undoped reference crystal. Two distinct PL bands were observed at low temperature (T = 8 K) for both crystals, located at 0.84 eV (D1) and 1.09 eV (D2) in this n-type Cl-doped Sb 2 Se 3 , while undoped Sb 2 Se 3 demonstrated PL bands at 0.89 eV (U1) and 1.02 eV (U2). The higher energy PL band at 1.09 eV (D2) is attributed to deep donor–deep acceptor (DD–DA) pair recombination, supported by its low thermal activation energy (42 ± 7 meV) and rapid quenching with increasing temperature. In contrast, the lower-energy PL band at 0.84 eV (D1) showed complex behavior, including a blueshift and a negative thermal quenching at low temperatures. This unique thermal and spectral behavior, which is absent in the undoped reference material, unequivocally links the recombination pathway to the extrinsic dopant. This emission is assigned to donor–acceptor pair recombination involving a deep acceptor and a Cl-induced shallow donor, likely corresponding to a Cl Se antisite defect as predicted previously by density functional theory calculations. These findings contribute to an improved understanding of the effect of external doping on this promising inorganic absorber material, Sb₂Se₃, for photovoltaic applications. • Defect-related recombination in Cl-doped Sb₂Se₃ studied by PL spectroscopy • PL band at 1.09 eV is assigned to deep donor–deep acceptor recombination • PL band at 0.84 eV arises from donor–acceptor recombination involving a Cl Se donor • A radiative recombination model for Cl-doped Sb₂Se₃ is proposed