Multi-Point Collaborative Passivation of Surface Defects for Efficient and Stable Perovskite Solar Cells

Abstract

The inherent defects (lead iodide inversion and iodine vacancy) in perovskites cause non-radiative recombination and there is also ion migration, decreasing the efficiency and stability of perovskite devices. Eliminating these inherent defects is critical for achieving high-efficiency perovskite solar cells. Herein, an organic molecule with multiple active sites (4,7-bromo-5,6-fluoro-2,1,3-phenylpropyl thiadiazole, M4) is introduced to modify the upper interface of perovskites. When M4 interacts with the perovskite surface, the active bromine (Br) site interacts with lead (Pb) at the surface to repair iodine atomic vacancy defects. The fluorine (F) site of M4 interacts with Pb to correct octahedral crystal lattice distortions and eliminate Pb_I defects. Additionally, sulfur–iodine (S–I) interactions reduce I–I dimerization and eliminate I_Pb defects. It is also calculated that the energy level of M4 aligns with the band gap, promoting charge transfer. As a result, the perovskite devices achieve an efficiency of 25.1%, a stabilized power output (SPO) of 25.0%, a voltage of 1.19 V, and a fill factor of 85.2%. The device retains 95% of its initial efficiency after 2000 h of ageing in a nitrogen atmosphere. Thus, multi-point cooperative passivation of surface defects provides an effective method to improve the efficiency and stability of perovskite solar cells.