Revealing the Role of Hydrogen in Highly Efficient Ag-Substituted CZTSSe Photovoltaic Devices: Photoelectric Properties Modulation and Defect Passivation

• The Ag/H co-doping strategy effectively suppresses SnZn-related defects and enhances the performance of CZTSSe solar cells. • Hydrogen incorporation improves the poor electrical conductivity and low carrier density caused by Ag substitution. • The synergistic effect of defect passivation and photoelectric property modulation leads to a champion efficiency of 14.74%. • This work provides a promising pathway for achieving high-efficiency kesterite-based photovoltaic devices.