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

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(Sx,Sey)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(Sx,Sey)3. The formation of Sb2(Sx,Sey)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(S0.55,Se0.45)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.