Sodium ion modulation for interface engineering in high-efficiency Sb₂(S,Se)₃ solar cells

Antimony selenosulfide [Sb₂(S,Se)₃] solar cells fabricated via the hydrothermal process have garnered significant attention due to their exceptional optoelectronic properties. However, Sb₂(S,Se)₃ thin films continue to encounter obstacles, such as low crystallinity, rough surface morphology, and uneven elemental distribution, all of which impede device performance. This study introduces sodium chloride (NaCl) as an interfacial modification layer to enhance the crystallinity, morphology, defect density, and overall optoelectronic performance of the films. NaCl post-treatment improves the crystallinity, reduces the defect density, and refines the surface morphology. Water contact angle measurements decreased from 69.63° to 53.63°, demonstrating enhanced hydrophilicity, which promotes uniform hole transport layer deposition and reduces pinholes. Electrochemical impedance spectroscopy shows an increase in recombination resistance (R_rec) from 4.2 to 4.8 kΩ, indicating reduced carrier recombination and improved charge transport efficiency at the interface. Ultimately, NaCl post-treatment enhanced the power conversion efficiency of Sb₂(S,Se)₃ solar cells from 6.63 to 8.30%, illustrating the effectiveness of this modification in optimizing the performance of Sb₂(S,Se)₃ solar cells.