Nonlinear defect interactions and performance limitations in Sb2Se3 solar cells: a factorial SCAPS-1D sensitivity analysis

Despite considerable efforts, efficiencies of Sb 2 Se 3 solar cells remain on a plateau limited by voltage deficits and carrier collection losses. Here, a SCAPS-1D model calibrated to the current record-efficiency Sb 2 Se 3 solar cell is used for full-factorial sensitivity analysis to understand and quantify the joint impact of representative donor, acceptor, double donor-like, and band tail defects, complemented by a selective-reduction analysis of the CdS/Sb 2 Se 3 interface defects. The simulations reveal, for the calibrated parameter set, a co-limited regime governed by a statistically significant, non-additive interaction between double donor-like and band tail defects. Band tail states, commonly associated with structural disorder, emerge as the dominant bulk voltage-limiting defect by reducing quasi-Fermi level splitting and enhancing distributed non-radiative recombination, degrading the device gradually without a critical threshold. Double donor-like defects control carrier extraction through compensation of the native p-type absorber: when their ionized charge exceeds the acceptor density, the junction field reverses at ∼10 15 cm -3 and carrier collection collapses, a threshold that shifts by more than an order of magnitude in the presence of band tail states. Near open circuit, recombination at the CdS/Sb 2 Se 3 interface dominates, and its passivation offers the largest single efficiency gain. We show that the defect interactions create a two-dimensional performance landscape in Sb 2 Se 3 , where band tail recombination and donor compensation act through different physical pathways and jointly limit the efficiency of the calibrated device. The resulting two-dimensional defect-tolerance map provides quantitative practical guidelines for defect engineering and further efficiency improvements of Sb 2 Se 3 solar cells.