biostudies-literatureUnknown18(1)Zheng XThe introduction of two-dimensional (2D) perovskite layers on top of three-dimensional (3D) perovskite films enhances the performance and stability of perovskite solar cells (PSCs). However, the electronic effect of the spacer cation and the quality of the 2D capping layer are critical factors in achieving the required results. In this study, we compared two fluorinated salts: 4-(trifluoromethyl) benzamidine hydrochloride (4TF-BA·HCl) and 4-fluorobenzamidine hydrochloride (4F-BA·HCl) to engineer the 3D/2D perovskite films. Surprisingly, 4F-BA formed a high-performance 3D/2D heterojunction, while 4TF-BA produced an amorphous layer on the perovskite films. Our findings indicate that the balanced intramolecular charge polarization, which leads to effective hydrogen bonding, is more favorable Nano-micro letters62https://www.ebi.ac.uk/biostudies/studies/S-EPMC12420534biostudies-literatureDifferentiating the 2D Passivation from Amorphous Passivation in Perovskite Solar Cells.PMC12420534Yan LHan PTang ZZheng XAhmed SLu DShi TKhan DXu GWang JTang JLiu ZZhang YChen WWang XfalseDifferentiating the 2D Passivation from Amorphous Passivation in Perovskite Solar Cells.The introduction of two-dimensional (2D) perovskite layers on top of three-dimensional (3D) perovskite films enhances the performance and stability of perovskite solar cells (PSCs). However, the electronic effect of the spacer cation and the quality of the 2D capping layer are critical factors in achieving the required results. In this study, we compared two fluorinated salts: 4-(trifluoromethyl) benzamidine hydrochloride (4TF-BA·HCl) and 4-fluorobenzamidine hydrochloride (4F-BA·HCl) to engineer the 3D/2D perovskite films. Surprisingly, 4F-BA formed a high-performance 3D/2D heterojunction, while 4TF-BA produced an amorphous layer on the perovskite films. Our findings indicate that the balanced intramolecular charge polarization, which leads to effective hydrogen bonding, is more favorable 2025-01-01T00:00:00Z2025 Sep2026-06-03T05:49:18.903Z2026-04-25T03:15:21.737ZS-EPMC124205344092423510.1007/s40820-025-01913-y