High-Performance CsPbX₃ Perovskite Quantum-Dot Light-Emitting Devices via Solid-State Ligand Exchange

Recently, all-inorganic perovskite quantum dots (PeQDs), CsPbX 3 have become attractive because of their excellent optoelectronic properties and superior air/moisture stabilities compared with conventional organic–inorganic hybrid perovskites, and the application of CsPbX 3 PeQDs to light-emitting devices (LEDs) has also become competitive. To enable the use of CsPbX 3 PeQDs for thin-film-type perovskite quantum-dot LEDs (PeQLEDs), a paradox associated with the ligand property and surface passivation must be overcome during thin-film fabrication. A decline in the photoemission performance was observed at relatively low amounts of surface-passivating ligands, while the quality of the thin film deteriorated in the presence of excessive ligands. To address this conflict, in this study, the performance of PeQLEDs based on CsPbX 3 fabricated by a novel method involving solid-state ligand exchange (SLE) with aromatic acid/amine was investigated. Using this strategy, most of the excess ligands were removed while preserving the surface passivation of CsPbX 3 in the thin film. We discovered that an optimal aromatic acid/amine ligand ratio is required for CsPbX 3 -based PeQLEDs to retain the solubility of the PeQDs and simultaneously accomplish the SLE process without affecting the properties of the PeQD. Moreover, an improvement in the overall photoemission efficiency of the resulting PeQLED device was confirmed under red, green, and blue conditions. In addition, a luminance of 1889 cd/m 2 and a current efficiency of 6.28 cd/A was achieved for the PeQLED.