Hydrothermal deposition of antimony selenosulfide thin films enables solar cells with 10% efficiency

Antimony chalcogenides are emerging photovoltaic materials, yet difficulties in fabricating high-quality films limit device performance. We show that hydrothermal synthesis affords good morphology and reduced defects in antimony selenosulfide films, enabling solar cells with an efficiency of 10%. Antimony selenosulfide, Sb-2(S,Se)(3), has attracted attention over the last few years as a light-harvesting material for photovoltaic technology owing to its phase stability, earth abundancy and low toxicity. However, the lack of a suitable material processing approach to obtain Sb-2(S,Se)(3)films with optimal optoelectronic properties and morphology severely hampers prospects for efficiency improvement. Here we demonstrate a hydrothermal approach to deposit high-quality Sb-2(S,Se)(3)films. By varying the Se/S ratio and the temperature of the post-deposition annealing, we improve the film morphology, increase the grain size and reduce the number of defects. In particular, we find that increasing the Se/S ratio leads to a favourable orientation of the (Sb4S(e)(6))(n)ribbons (S(e) represents S or Se). By optmizing the hydrothermal deposition parameters and subsequent annealing, we report a Sb-2(S,Se)(3)cell with a certified 10.0% efficiency. This result highlights the potential of Sb-2(S,Se)(3)as an emerging photovoltaic material.