High-performance all-inorganic perovskite light-emitting diodes enabled by a self-assembled molecule additive via defect passivation and strain relaxation

All-inorganic perovskite light-emitting diodes (AIPeLEDs) have been demonstrated with superior thermal stability than organic analogues, but the high defect density and lattice strain of all-inorganic perovskites commonly result in compromised efficiency and stability of the devices. Herein, a self-assembled molecule, 4-bromobenzoic acid (BBA), is adopted as an additive to modify CsPbBr3-based green AIPeLEDs. In particular, the formic acid group (-COOH) of BBA can interact with the uncoordinated Pb dangling bonds, leading to reduced defects and released lattice strain of perovskites, thereby facilitating the formation of all-inorganic perovskite films with a high photoluminescence quantum yield of 54.5 %. As a result, AIPeLEDs with a high maximum current efficiency of 42.4 cd A-1, and an external quantum efficiency of 11.4 % are obtained. Moreover, promoted by the inhibited non-radiative recombination and released lattice stress, the T50 lifetime (at an initial brightness of 200 cd m-2) is also improved from 2 h for the control PeLEDs to 8 h for the BBA-treated PeLEDs, which further confirms the superiority of BBA in passivating the AIPeLEDs.