Additive engineering by tetrabutylammonium iodide for antimony selenosulfide solar cells

Antimony selenosulfide (Sb 2 (S,Se) 3 ) solar cells have attracted great attention due to their tunable optoelectronic properties, ease of preparation and low toxicity. However, the harmful intrinsic defect density and internal nonradiative recombination of Sb 2 (S,Se) 3 hinder its practical usage. In this work, a facile additive approach is explored to modify the Sb 2 (S,Se) 3 solar cell efficiency by using tetrabutylammonium iodide (TBAI). After applying a certain amount of TBAI into the Sb 2 (S,Se) 3 precursor solution, the film surface presents lower cracks and roughness than that of the pristine sample. It also increases its hydrophobicity and n-type nature revealed by contact angle and work function measurements. Moreover, the incorporation of TBAI during the formation of the Sb 2 (S,Se) 3 layer improves the quality of the film effectively suppresses its defect trap density, which manifests as a reduction in charge recombination and enhancement of the power conversion efficiency (PCE) when incorporated into solar cells. The fabricated device with 0.62 mol% of TBAI shows the highest PCE (8.87%) and high stability without encapsulation, maintaining about 91% of its initial efficiency after 60 d in air. The results provide a feasible strategy to the ongoing progress of reliable Sb 2 (S,Se) 3 devices.