In recent years, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has witnessed rapid progress. Nevertheless, the pervasive defects prone to non-radiative recombination and decomposition exist at the surface and the grain boundaries (GBs) of the polycrystalline perovskite films. Herein, we report a comprehensive dual-passivation (DP) strategy to effectively passivate the defects at both surface and GBs to enhance device performance and stability further. Firstly, a fluorinated perylene-tetracarboxylic diimide derivative is permeated in the perovskite metaphase during antisolvent treatment, and then a fluorinated bulky aromatic ammonium salt is introduced over the annealed perovskite. The reduction of defect density can be unambiguously proved by the superoxide species generation/quenching reaction. As a result, optimized planar PSCs demonstrate a decreased open-circuit voltages deficit from 0.47 to 0.39 V and the best efficiency of 23.80 % from photocurrent scanning with a stabilized maximum power output efficiency of 22.99 %. Without encapsulation, one typical device can maintain over 85 % of the initial efficiency after heating on a hot plate at 100 °C for 30 h under relative humidity (RH) of 70 %. When the device is aged under 30±5 % RH, over 97 % of its initial PCE is retained after 1700 h.
Keywords: defects; dual-passivation; perovskite solar cells; stability; superoxide.
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