Additive engineering by tetrabutylammonium iodide for antimony selenosulfide solar cells

Antimony selenosulfide (Sb2(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 Sb2(S,Se)3 hinder its practical usage. In this work, a facile additive approach is explored to modify the Sb2(S,Se)3 solar cell efficiency by using tetrabutylammonium iodide (TBAI). After applying a certain amount of TBAI into the Sb2(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 Sb2(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 Sb2(S,Se)3 devices.