Ions‐induced Assembly of Perovskite Nanocomposites for Highly Efficient Light‐Emitting Diodes with EQE Exceeding 30

Metal halide perovskites, a cost‐effective class of semiconductos, hold great promise for display technologies that demand high‐efficiency, color‐pure light‐emitting diodes (LEDs). Early research on three‐dimensional (3D) perovskites showed low radiative efficiencies due to modest exciton binding energies. To inprove luminescence, reducing dimensionality or grain size has been a common approach. However, dividing the perovskite lattice into smaller units may hinder carrier transport, compromising electrical performance. Moreover, the increased surface area introduce additional surface trap states, leading to greater non‐radiative recombination. Here, an ions‐induced growth method is employed to assembe lattice‐anchored perovskite nanocomposites for efficient LEDs with high color purity. This approach enables the nanocomposite thin films, composed of 3D CsPbBr3 and its variant of zero‐dimensional (0D) Cs4PbBr6, to feature significant low trap‐assisted nonradiative recombination, enhanced light out‐coupling with a corrugated surface, and well‐balanced charge carrier transport. Based on the resultant 3D/0D perovskite nanocomposites, the perovskite LEDs (PeLEDs) achieving an remarkable external quantum efficiency of 31.0% at the emission peak of 521 nm with a narrow full width at half‐maximum of only 18 nm. This sets a new benchmark for color purity in high performance PeLED research, highlighting the significant advantage of this approach. This paper presents an ions‐induced crystallization method to synthesize perovskite dual‐phase nanocomposites of CsPbBr3 and Cs4PbBr6. This approach enlarges grain sizes, reduces trap density, and improves both light extraction efficiency and electrical characteristics. Consequently, green perovskite light‐emitting diodes with a maximum external quantum efficiencie exceeding 30% and a narrow full width at half‐maximum of 18 nm are achieved.