Sodium Metavanadate Chelation‐Assisted Chemical Bath Deposition to High‐Efficiency Antimony Selenosulfide Solar Cells

Fabricating light‐harvesting layers with compact and flat morphology, high purity, and minimal deep‐level defects is crucial for achieving high‐efficiency thin‐film solar cells. Antimony selenosulfide (Sb 2 (S,Se) 3 ), showing excellent optoelectronic properties and tunable bandgap, has become one of the promising emerging photovoltaic materials. Owing to advancements in solution processing of films, the device efficiency has been boosted to 10%. To further improve the device performance, regulating reaction kinetics to deposit thin films with enhanced morphology and high purity is critical. Herein, a sodium metavanadate (NaVO 3 ) chelation‐assisted strategy is developed to control the chemical bath deposition (CBD) fabrication of Sb 2 (S,Se) 3 films. In the synthesis, the decavanadate ion (HV 10 O 28 5− ), generated through condensation reactions of NaVO 3 , chelates with SbO + , thereby regulating unexpected rapid nucleation kinetics. This modified deposition process generates Sb 2 (S,Se) 3 films with large grain size and uniform morphology. Moreover, the new deposition kinetics is found to alleviate the appearance of two kinds of deep‐level defects, Sb S1 and Sb S3 . Finally, the improvements in morphological, crystal, and electrical properties enable the Sb 2 (S,Se) 3 solar cell reaching a 10.15% efficiency, which is the champion efficiency for CBD‐fabricated Sb 2 (S,Se) 3 photovoltaic devices. This cation braking strategy establishes fundamental guidelines for morphology optimization and defect control of Sb 2 (S,Se) 3 films.