Triple-cation perovskite solar cells show concentration-dependent defect passivation by phenethylammonium iodide

Incorporation of bulky organic ammonium additives into perovskite precursor solutions often induces low-dimensional phase formation, which can improve interfacial passivation but may hinder intrinsic charge-transport pathways. Here, we investigate the incorporation of low-concentration phenethylammonium iodide (PEAI) for suppressing defect-assisted recombination while preserving the predominantly three-dimensional (3D) perovskite framework in Cs 0.175 FA 0.750 MA 0.075 Pb(I 0.880 Br 0.120 ) 3 perovskite solar cells. The low-concentration regime is defined as PEAI concentrations of ≤0.75 wt %. Structural analyses show no detectable diffraction features associated with low-dimensional phases within this range. Optical and electrical analyses indicate reduced defect-assisted recombination, with the average carrier lifetime increasing from 94.53 to 206.46 ns and the trap density decreasing from 1.68 × 10 16 to 1.12 × 10 16 cm −3 . The 0.50 wt % PEAI device achieves a power conversion efficiency (PCE) of 20.98% and shows improved damp-heat (DH) stability relative to the control.