TY  - EJOU
AU  - Wen, Yunpeng 
AU  - Ke, Bingyang 
AU  - Ding, Junrong 

TI  - Active Learning-Driven Optimization of Sulfurization–Selenization Processes in Sb<sub>2</sub>(S,Se)<sub>3</sub> Thin Films for Enhanced Photovoltaic Efficiency
T2  - Chalcogenide Letters

PY  - 2026
VL  - 23
IS  - 1
SN  - 1584-8663

AB  - This study reports an active learning (AL)-guided strategy to optimize the sulfurization–selenization processing conditions of Sb<sub>2</sub>(S,Se)<sub>3</sub> thin-film photovoltaic absorbers for enhanced power conversion efficiency (PCE). By coupling Gaussian process modeling with iterative experimental feedback, we explored 20 targeted annealing conditions across the full compositional spectrum (x = 0–1) and identified an optimal S/(S + Se) ratio of 0.40 (x = 0.60), which yielded a band gap (Eg) of ~1.34 eV, close to the theoretical Shockley–Queisser optimum. The optimized process employed a controlled two-step 420°C anneal with sequential H<sub>2</sub>Se→H<sub>2</sub>S exposure, which produced large plate-like grains (300–500 nm) with columnar cross-sectional morphology and eliminated the ribbon-like anisotropy typical of pure Sb<sub>2</sub>Se<sub>3</sub>. XRD confirmed a single-phase orthorhombic structure with no secondary phases, while EDS mapping showed homogeneous S/Se distribution and a mild back-surface S gradient. Optical absorption coefficients exceeded 10<sup>5</sup> cm<sup>−</sup><sup>1</sup> (hν &gt; 1.7 eV), and photoluminescence revealed a reduced Stokes shift (~40 meV) and low Urbach energy (~20 meV), indicating suppressed defect states. Devices fabricated with a Zn(O,S) buffer achieved average metrics of Voc = 0.58 V, Jsc = 25.0 mA cm<sup>−</sup><sup>2</sup>, FF = 78%, and PCE = 12.2%, representing a ~62% relative improvement over our baseline Sb<sub>2</sub>Se<sub>3</sub> cells (7.5%). The EQE exceeded 90% across 400–900 nm, and the integrated Jsc matched measured values within 5%. Preliminary stability tests retained 95% of initial PCE after 100 h under 1-sun illumination at 45°C. These findings establish AL-driven exploration as a powerful method for rapidly converging on high-performance chalcogenide processing regimes.
KW  - Grain coarsening; defect suppression; optical absorption; compositional gradient; photovoltaic stability

DO  - 10.32604/cl.2026.076587