Anion-Vacancy Defect Passivation for Efficient Antimony Selenosulfide Solar Cells via Magnesium Chloride Post-growth Activation

The quasi-1D antimony selenosulfide (Sb 2 (S,Se) 3 ) light-harvesting material has attracted tremendous attention for photovoltaic applications because of its superior materials and optoelectronic properties. However, one of the critical obstacles faced by Sb 2 (S,Se) 3 solar cells is the presence of many defects in absorbers, especially those deep-level anion-vacancy defects which are prone to serving as recombination centers. In this work, an effective defect engineering strategy via magnesium chloride (MgCl 2 ) postgrowth activation is explored for high performance antimony selenosulfide solar cells. Through careful characterization of structural, morphological, and defect properties, as well as the photovoltaic performance, complemented with firs-principle calculations, it is revealed that this postgrowth activation step enables the effective passivation of deep-level anion-vacancy defects via electrical chloride-doping, the recrystallization of small grains for producing large-grained films, and the formation of favorable cascade energy levels to promote the charge transport. Benefitting from suppressed charge recombination and facilitated charge transport, the Sb 2 (S,Se) 3 solar cells yield a considerable power conversion efficiency of 10.55%, which is among the top efficiencies reported for antimony chalcogenide solar cells. This study underscores the significance of anion-vacancy passivation for efficient antimony chalcogenide devices.