Simple Ball‐Milled Molybdenum Sulfide Nanosheets for Effective Interface Passivation with Self‐Repairing Function to Attain High‐Performance Perovskite Solar Cells

Interface defects can generate serious nonradiative recombination in perovskite solar cells (PSCs) and need to be restrained for further optimization of device performance. Herein, common and easily available 2D MoS 2 nanosheets prepared by a ball‐milled method are demonstrated. The obtained MoS 2 has bigger specific surface area and narrower pore distribution, inducing more water to be trapped on the surface or in pores of MoS 2 . With annealing, the locally absorbed water can be desorbed, and much more Mo atoms at the outermost surface layers could bond with oxygen to repair the uncoordinated Mo at edge sites for more ordered Mo—S—Mo bonds, which can weaken the catalytic activity of MoS 2 to stabilize the heterojunction interface of hole transport layer (HTL)/perovskite. When it is used as the passivation layer between HTL and perovskite, the Mo 2+ –Mo 4+ ion pair can promote electron transfer from Pb ° to I ° , suppressing the deep defects at this interface near the perovskite side. Meanwhile, MoS 2 can passivate the surface (or grain boundaries) defects through the bond of Mo—I or Pb—O. The resultant PSCs give a champion efficiency of 22.39% with MoS 2 treatment, thus enabling the decorated devices with excellent long‐term stability.