High-Efficiency Flexible Sb₂Se₃ Solar Cells by Back Interface and Absorber Bulk Deep-Level Trap Engineering

The unique one-dimensional crystal structure and low-temperature growth techniques make antimony selenide (Sb2Se3) a promising potential material for flexible and lightweight photovoltaic applications. The buried Sb2Se3/molybdenum back-contact interface is the main obstacle to high-efficiency flexible Sb2Se3 solar cells in a substrate configuration. To improve the crystalline quality of Sb2Se3 and enhance hole extraction, we introduce a new lead selenide (PbSe) transition layer, fabricated at room temperature, at the back-contact interface. The concomitant incorporation of tiny amounts of Pb into the Sb2Se3 readily reduces the formation of undesired deep-level traps. The champion device on a flexible polyimide (PI) foil yields a power-conversion-efficiency of 8.43%, which is a record efficiency in flexible Sb2Se3 photovoltaics. This work highlights the synergistic effect of the PbSe interlayer at the buried back-contact interface and its effect on the bulk absorber. This method provides a complete low-temperature vacuum-vapor-fabrication process for high-efficiency flexible Sb2Se3 solar cells in the substrate configuration.