Dual-functional Amino–Sulfonic acid interfacial passivation for efficient perovskite solar cells

Interfacial defect passivation is essential for suppressing non-radiative recombination (NRR) and charge accumulation, which limit the performance of inverted perovskite solar cells (PSCs). Herein, we introduce DSDA (4,4′-diamino-2,2′-stilbenedisulfonic acid) as a multifunctional interfacial modifier between a triple-cation perovskite absorber and the electron transport layer (ETL). The amino (-NH 2 ) and sulfonic acid (-SO 3 H) groups of DSDA effectively coordinate with undercoordinated lead (Pb 2+ ) ions and passivate halide vacancy defects, as verified by DFT (density functional theory), XPS (X-ray photoelectron spectroscopy), and FTIR (Fourier-transform infrared spectroscopy). Surface characterization demonstrates that optimized DSDA treatment improves grain growth, reduces surface roughness, and suppresses defect-assisted recombination. Ultraviolet photoelectron spectroscopy (UPS) further reveals a favorable n-type energy level shift, promoting efficient charge extraction and reduced interfacial charge accumulation. Consequently, the optimized device achieves a PCE (power conversion efficiency) of 20.1%, significantly outperforming the untreated control (16.0%). Moreover, the optimized DSDA-treated device exhibits enhanced stability, retaining 63% of its initial PCE after 720 h under room temperature conditions without encapsulation. This study highlights DSDA interfacial engineering as an effective strategy for developing high-efficiency inverted PSCs.