Ag-Induced Phase and Defect Engineering of Co-Evaporated Sb2Se3 Thin Films for Enhanced Photovoltaic Performance

Abstract

High-efficiency antimony selenide (Sb2Se3) solar cells remain limited by anisotropic charge transport, high defect density, and rapid back-contact recombination. We demonstrate a simple co-evaporation strategy for introducing an ultrathin Ag interlayer at the Sb2Se3/Mo interface. The proposed strategy significantly enhances the performance of the fabricated devices. Incorporation of an Ag layer promotes grain growth, improves crystallinity, and passivates bulk defects, thereby suppressing interfacial recombination and enhancing both the open-circuit voltage and fill factor. Structural analyses reveal an orientation transition of the quasi-one-dimensional orthorhombic Sb2Se3 ribbons from a preferred (hk1) orientation to a random one. This transition is driven by the sequential reaction of Ag with Se to form Ag2Se, which subsequently reacts with Sb2Se3 to yield AgSbSe2. However, when the Ag content exceeds the optimal level, unreacted Ag2Se accumulates at the bottom of the film, degrading device performance. Time-resolved photoluminescence and capacitance measurements confirm reduced defect densities and optimized junction properties. The optimized Sb2Se3 device incorporating the Ag interlayer achieves a power conversion efficiency of 5.56%, outperforming the Ag-free counterpart under standard AM 1.5G illumination. The proposed strategy offers a promising route to high-performance Sb2Se3 thin-film photovoltaics and provides a pathway for tandem integration of Sb2Se3-based devices.