Grain Boundary Defect Controlling of Perovskite via N‐Hydroxysuccinimide Post‐Treatment Process in Efficient and Stable n–i–p Perovskite Solar Cells

Nonradiative recombination on perovskite surface and grain boundary largely constrains the efficiency and stability of photovoltaic devices. Surface passivation has proven to be the most effective strategy to suppress photogenerated carrier recombination. Herein, functional N ‐hydroxysuccinimide (NHS) is incorporated in perovskite films by suppressing nonradiative losses both in surface and in grain boundary. The NHS molecules are located at the perovskite grain boundary and surface with good compability with the perovskite crystal network, which forms an effective barrier at the grain boundary to prevent the permeation of moisture. Equally important, the interactions between the CO group in NHS and perovskite undercoordinated groups (Pb 2+ or Pb clusters) reduce the surface defects of the perovskite, yielding a minimal energy loss. The prolonged lifetime of carriers with NHS‐treated perovskites prevents the carrier quenching at the perovskite grain boundary and interface. As a result, open‐circuit voltage of the solar cell is up to 1.13 V with a power conversion efficiency (PCE) of 22.21%. The stability of the device is also significantly improved, wherein devices with NHS retain 81% of the initial PCE after 1000 h at room temperature.