Spontaneous surface/interface ligand-anchored functionalization for extremely high fill factor over 86% in perovskite solar cells

The efficiency and stability of perovskite solar cells (PSCs) are hampered by the undesirable charge recombination on defective surface of polycrystalline perovskite grains and inferior charge transfer at relevant contact interfaces. Herein, we discovered that spontaneous anchoring of long-chain oleylamine (OA) ligands onto perovskite film surface can simultaneously improve the efficiency and stability of PSCs made by scalable blade-coating. The ultrathin insulating OA layer on perovskite film surface can achieve an ingenious surface/interface functionalization that plays synergistic roles in effective defect passivation and efficient charge tunneling. Blade-coated PSCs with OA functionalization acquire champion power conversion efficiencies (PCEs) of 21.5%, accompanied by a surprisingly high fill factor up to 86.3%, which can be ascribed to the reduced series resistance, facilitated electron tunneling and suppressed interfacial charge recombination at relevant interface. The OA-functionalized perovskite film is much more resistant to moisture, and improves the device shelf lifetime to >1000 h, and operation stability to >500 h under continuous one sun illumination with 96% initial efficiency retained.