4-Trifluorophenylammonium Iodide-Based Dual Interfacial Modification Engineering toward Improved Efficiency and Stability of SnO₂-Based Perovskite Solar Cells

Passivation engineering has been identified as an effective strategy to eliminate the targeted interfacial defects for improving the efficiency and stability of perovskite solar cells (PSCs). Herein, 4-trifluorophenylammonium iodide (CF 3 PhAI) is presented as a multifunctional passivation agent to modify buried SnO 2 /perovskite and perovskite/hole transport layer (HTL) interfaces. Upon incorporation of CF 3 PhAI between SnO 2 and perovskite, CF 3 PhAI can chemically link to SnO 2 via Lewis coordination and electrostatic coupling, thereby effectively passivating under-coordinated Sn and filling the oxygen vacancy. Meanwhile, CF 3 PhAI helps anchor PbI 2 and organic cations (MA + /FA + ) to control the crystallization of the perovskite. Consequently, reduced interfacial defects, homogeneous perovskite crystallites, and better energetic alignment can be simultaneously achieved. When CF 3 PhAI was further used to modify the perovskite/HTL interface, the fabricated PSCs yielded an impressive power conversion efficiency of 23.06% together with negligible J – V hysteresis. The unencapsulated devices exhibited long-term stability in wet conditions (91.8% efficiency retention after 1000 h) due to the water-resistant CF 3 PhAI. We also achieved good light soaking stability, maintaining 86.1% of its initial efficiency after aging for 720 h. Overall, our finding provides a promising strategy for modifying the dual contact interfaces of PSCs toward improved efficiency and stability.