Hard and soft Lewis‐base behavior for efficient and stable CsPbBr <sub>3</sub> perovskite light‐emitting diodes
Changjiu Sun, Keyu Wei, Jian Zhao, Yuanzhi Jiang, Yilong Wang, Haiqing Hu, Xin Wang, Yongqin Zhang, Mingjian Yuan
Abstract
Abstract All‐inorganic CsPbBr 3 perovskite is an attractive emission material for high‐stability perovskite light‐emitting diodes (PeLEDs), due to the high thermal and chemical stability. However, the external quantum efficiencies (EQEs) of CsPbBr 3 based PeLEDs are still far behind their organic–inorganic congeners. Massive defect states on the surface of CsPbBr 3 perovskite grains should be the main reason. Lewis base additives have been widely used to passivate surface defects. However, systematic investigations which relate to improving the passivation effect via rational molecule design are still lacking. Here, we demonstrate that the CsPbBr 3 film’s optical and electrical properties can be significantly boosted by tailoring the hardness–softness of the Lewis base additives. Three carboxylate Lewis bases with different tail groups are selected to in‐situ passivate CsPbBr 3 perovskite films. Our research indicates that 4‐(trifluoromethyl) benzoate acid anion (TBA − ) with the powerful electron‐withdrawing group trifluoromethyl and benzene ring possesses the softest COO − bonding head. TBA − thus acts as a soft Lewis base and possesses a robust combination with unsaturated lead atoms caused by halogen vacancies. Based on this, the all‐inorganic CsPbBr 3 PeLEDs with a maximum EQE up to 16.75% and a half‐lifetime over 129 h at an initial brightness of 100 cd m −2 is thus delivered.