Octylammonium Sulfate Decoration Enhancing the Moisture Durability of Quasi‐2D Perovskite Film for Light‐Emitting Diodes

Abstract Quasi‐2D perovskite exhibits excellent luminescence properties for highly efficient perovskite light‐emitting diodes (PeLEDs). However, the lattice degradation and crystalline phase transition induced by water limit the PeLED's development for application and commercialization. It is demonstrated that the organic additives effectively reduce the defect density, while the bonding strength of these organics and perovskite becomes weak under the high electric field and the Joule heat in an operating PeLED. Thus, an alternative additive for forming strong bonding with perovskite is promising to improve the stability of perovskite film and PeLEDs simultaneously. Here, it is shown that octylammonium sulfate decoration effectively enhances the moisture durability of PEA 2 (CsPbBr 3 ) 4 PbBr 4 quasi‐2D perovskite film by generating PbSO 4 on the surface. The strong bonding interaction of SO 4 2− and Pb 2+ ions leads to the reduced defect density, enhanced lattice stability, and robust photoluminescence quantum yield of perovskite film, which is confirmed by the density functional theory calculation. Moreover, the generated PbSO 4 reduces the internal resistance and adjusts the band structure of perovskite film to enhance the carrier transport and injection balance. The PeLEDs based on PbSO 4 decorated perovskite film exhibit enhanced operational lifetime and the maximum external quantum efficiency of 10.84%.