Chemical insight into the hydrothermal deposition of Sb2(S,Se)3 towards delicate microstructure engineering

Abstract

Hydrothermal deposition is an ideal method to fabricate high-efficiency antimony sulfoselenide (Sb₂(S,Se)₃) solar cells due to its simple, eco-friendly and low-cost processing characteristics. This deposition approach has enabled efficiency breakthrough in Sb₂(S,Se)₃ solar cells, while the chemical mechanisms in the deposition and annealing processes remain undiscovered. Here, we reveal that the deposition and annealing of hydrothermally deposited Sb₂(S,Se)₃ are essentially driven by antimony polysulfoselenide (Sb₂(S_x,Se_y)₃ (x + y > 1)) and antimony sulfoselenide (Sb₂(S,Se)₃) amorphous nanocrystals. On the grounds of elemental, thermogravimetric and defect analyses, we identify a new intermediate phase composed of Sb₂(S_x,Se_y)₃. The formation of Sb₂(S_x,Se_y)₃ and the consequent mass loss during the post-annealing process are found to produce poor microstructural performance in the Sb₂(S,Se)₃ absorber layer (i.e., pinholes), which leads to the disruption of internal orderliness. Encouragingly, we found that the introduction of a zeolite can effectively improve the compactness of the Sb₂(S_0.55,Se_0.45)₃ film by altering the pH of the hydrothermal solution, which in turn leads to a power conversion efficiency of 8.87%, which shows a promising improvement of more than 21.8% compared with the traditional preparation method. This study offers fundamental insights into the hydrothermal deposition-derived Sb₂(S,Se)₃ solar cells, and provides a simple and effective method for improving the device performance.