Realizing High‐Efficiency Perovskite Solar Cells by Passivating Triple‐Cation Perovskite Films

The photovoltaic performance of perovskite solar cells (PSCs) prepared by the low‐temperature solution method has made rapid progress. However, the surface of the film is prone to defects that trap photogenerated charges, resulting in nonradiative recombination energy loss and limiting the open‐circuit voltage and overall performance of the device. Interface passivation as an effective method can significantly reduce defects and inhibit nonradiative recombination. Herein, a simple method is introduced to passivate perovskite films by a carboxylated (–COOH) sensitizer that is applied in dye‐sensitized solar cells (DSCs), 4‐(bis(9,9‐dimethyl‐9H‐flouren‐2‐yl)amino)‐1‐naphthoic acid (KTN) molecules. The research results show that the chemical interaction between KTN and iodide vacancies exposing Pb2+ can reduce the nonradiative recombination and elongate the carrier lifetime, which leads to an excellent power conversion efficiency (PCE) with 23% with an obvious increase in open‐circuit voltage (VOC) of 60 mV. Moreover, the defect passivation can significantly enhance the stability of corresponding PSC devices. The unencapsulated device with KTN passivation can readily maintain ≈90% of its initial efficiency value after 1400 h. These findings may provide a novel approach for interfacial defect passivation to further promote the performance and stability of PSCs.