Quantifying Deep‐Level Defects‐Dominated Degradation for Commercially Viable Perovskite Solar Cells

The unclear mechanisms and dominant types of defects causing degradation hinder the stability of perovskite solar cells, leading to increased operating costs and limiting their commercialization. In this study, we identify deep‐level I FA and I Pb defects as the primary cause of device degradation based on quantitative analysis of capacitance‐frequency spectra combined with detailed balance theory, although the concentrations are lower than those of commonly believed shallow‐level defects by three orders of magnitude. To mitigate these issues, we design a non‐intercalary ligand coordination strategy through dual‐end electropositive 3TU 2+ ions, which effectively passivated the degradation‐induced deep‐level defects. This approach results in a significant improvement in quasi‐Fermi level splitting alignment, reducing energy loss at the rear interface by an order of magnitude (from 1.46% to 0.62%). In addition to achieving a certified efficiency of 25.56%, our devices demonstrate an extrapolated T 80 lifetime exceeding 10 years, as per the ISOS‐LC‐1 protocol. This improvement reduces the levelized cost of energy to 0.148$ kWh −1 , on par with silicon photovoltaics, thus enhancing the commercial viability of perovskite solar cells.