Enhancing the Efficiency of Kesterite Solar Cells Through Ag Doping

Recent studies show that CZTSSe solar cells, made from abundant materials, achieve over 14% efficiency. CZTSSe lower efficiency is due to defects causing higher carrier recombination losses, mainly at the absorber-buffer interface. Introducing Ag into CZTSSe improves carrier mobility, lowers annealing temperatures, and enhances absorber quality by reducing Cu_Zn defects. This study investigates how the position of Ag in the precursor structure affects device performance. By adding a 5 nm Ag layer at various positions within the stacked precursor, it was found that placing Ag at the Zn-Mo interface significantly improved performance metrics, including efficiency, open-circuit voltage, current density, and fill factor. This improvement is attributed to the rapid formation of a Cu-Sn alloy, enhancing grain growth and reducing defects. Conversely, placing Ag between Cu and Zn hindered Cu-Zn alloy formation, leading to increased defects and recombination losses, worsened by a cliff-like band alignment at the absorber-CdS interface. Thus, the strategic positioning of Ag in the precursor structure is crucial for optimizing CZTSSe solar cell efficiency, providing valuable insights for future design improvements.

Acknowledge: This work was supported by the DGIST R&D programs of the Ministry of Science and ICT (25-ET-01).