Synergistic Bimolecular Passivation Enabling High-Performance Inverted Perovskite Solar Cells

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Abstract
Surface and interfacial defects represent the primary loss pathways limiting the power conversion efficiency (PCE) and the operational stability of inverted perovskite solar cells (PSCs). Here, we report a sequential bimolecular passivation strategy employing propane-1,3-diammonium diiodide (PDAI) followed by (E)-[(4-trifluoromethyl)styryl]phosphonic acid (4TF) to simultaneously mitigate grain boundary and surface-state traps. PDAI acts as a deep-level defect passivant by penetrating grain boundaries, effectively eliminating interfacial pinholes and inducing a Fermi level (EF) shift that reduces the work function (WF) from 4.40 to 4.28 eV. Subsequent 4TF treatment facilitates coordination bonding with undercoordinated Pb2+ sites, establishing a positive surface dipole that shifts the WF to 4.54 eV. This dual-functional approach optimizes band alignment with the C60 electron transport layer, while yielding a compact, pinhole-free morphology. Consequently, PSCs treated with PDAI/4TF deliver a champion PCE of 24.6%, significantly surpassing the PDAI-only (PCE = 23.17%) and control (PCE = 21.21%) devices. These findings underscore the effectiveness of combined defect and dipole control for tailoring the perovskite/ETL interface in high-performance perovskite solar cells.
Funding Information
  • Korea Institute of Energy Research (C6-2403-13)
  • Korea Institute of Energy Technology Evaluation and Planning (RS-2023-00302107)
  • World Bank Group

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