Single-Crystalline Antimony Sulfoselenide Microrods with Selenium Gradient Incorporation for High-Responsivity Photodetection

Antimony sulfide (Sb₂S₃) faces challenges in optoelectronics due to sulfur vacancy-induced recombination and crystallization heterogeneity. A two-step defect engineering strategy combining hydrothermal growth and postselenization treatment has been developed, enabling the fabrication of single-crystalline antimony sulfoselenide (Sb₂(S,Se)₃) microrods with suppressed defects and enhanced optoelectronic properties. Theoretical calculations confirm selenium passivation of sulfur vacancies is energetically favorable (-0.66 eV vs vacancy formation energy of 0.75 eV), promoting selective Se substitution at defect sites. The selenization temperature (300 ∼ 400 °C) has been controlled to achieve tunable Se gradient incorporation, which passivates vacancies while minimizing interfacial disorder. The optimized Sb₂(S,Se)₃ microrod photodetector exhibits a high responsivity of 9.68 A/W at 550 nm, an external quantum efficiency of 2185%, fast response times (4.0 ms rise and 3.8 ms decay), and a detectivity of 7.2 × 10¹⁰ Jones. Systematic characterizations and ab initio molecular dynamics simulations demonstrate that the optoelectronic performance enhancement arises from improved crystallinity, reduced defect density, and optimized carrier dynamics. This work presents a generalizable approach for defect engineering in low-dimensional metal chalcogenides through spatially controlled heteroatom doping, providing insights for the design of high-performance optoelectronic devices.