All-Inorganic Perovskite Quantum Dots Based on InX₃-Trioctylphosphine Oxide Hybrid Passivation Strategies for High-Performance and Full-Colored Light-Emitting Diodes

All-inorganic perovskite quantum dot (PeQD) light-emitting diodes (QLEDs) are promising candidates for the next-generation flat-panel displays and semiconductor lighting technology. However, the stability issues severely limit their commercial applications. In this study, highly stable CsPbX3 (X = Cl, Br, I) PeQD films were prepared using InX3 (X = Cl, Br, I) and trioctylphosphine oxide (TOPO) as inorganic–organic hybrid ligands to passivate the surface defects of PeQDs. The obtained InX3-TOPO-CsPbX3 PeQDs not only have high photoluminance quantum yields (PL QYs) and very narrow emission (14–35 nm) but also possess long-term stability. This is mainly due to the synergistic effect of InX3 and TOPO inorganic–organic surface ligand passivation, which can effectively inhibit the halogen vacancy and reduce the surface defect of PeQDs. In addition, the chemical states of InBr3-TOPO-CsPbBr3 PeQDs were analyzed by XPS technology and it was found that InX3-TOPO synergistic surface passivation can effectively reduce the Pb═O bond in the crystal lattice. Moreover, full-colored perovskite QLEDs based on InX3-TOPO-CsPbX3 PeQDs were achieved by using ZnO/PBD as the double electron transport layer, NiO/TFB as the double hole transport material, and InX3-TOPO-CsPbX3 PeQDs as the light-emitting layer. The EQE (%) and luminance (cd m–2) of red, green, and blue QLEDs based on these InX3-TOPO-CsPbX3 PeQDs were 8.2% and 9080 cd m–2, 7.8% and 18,600 cd m–2, and 1.62% and 164 cd m–2, respectively. This cooperative effect based on the InX3-TOPO hybrid passivation strategy will open a way for the preparation of highly efficient, stable, and color-tunable perovskite QLEDs.