Inverted (pin) perovskite solar cells (PSCs) afford improved operating stability in comparison to their nip counterparts but have lagged in power conversion efficiency (PCE). The energetic losses responsible for this PCE deficit in pin PSCs occur primarily at the interfaces between the perovskite and the charge-transport layers. Additive and surface treatments that use passivating ligands usually bind to a single active binding site: This dense packing of electrically resistive passivants perpendicular to the surface may limit the fill factor in pin PSCs. We identified ligands that bind two neighboring lead(II) ion (Pb ²⁺ ) defect sites in a planar ligand orientation on the perovskite. We fabricated pin PSCs and report a certified quasi–steady state PCE of 26.15 and 24.74% for 0.05– and 1.04–square centimeter illuminated areas, respectively. The devices retain 95% of their initial PCE after 1200 hours of continuous 1 sun maximum power point operation at 65°C.

Perovskite solar cells retain their performance with temperature cycling using a compliant, ethylene vinyl acetate encapsulant.

Although buckminsterfullerene (C ₆₀ ) is usually the electron transport layer (ETL) in inverted perovskite solar cells (PSCs), its molecular nature leads to weak interfaces that result in nonideal interfacial electronic and mechanical degradation. In this study, we synthesized an ionic salt from C ₆₀ , 4-(1′,5′-dihydro-1′-methyl-2′ H -[5,6] fullereno-C ₆₀ - I _h -[1,9-c]pyrrol-2′-yl) phenylmethanaminium chloride (CPMAC), and used it as the electron shuttle in inverted PSCs. The CH ₂ -NH ₃ ⁺ head group in the CPMA cation improved the ETL interface, and the ionic nature enhanced the packing, leading to a ~threefold increase in the interfacial toughness compared with that of C ₆₀ . Using CPMAC, we obtained ~26% power conversion efficiencies (PCEs) with ~2% degradation after 2100 hours of 1-sun operation at 65°C. For minimodules (four subcells, 6 square centimeters), we achieved a PCE of ~23% with <9% degradation after 2200 hours of operation at 55°C.