  Metal halide perovskites, a class of cost-effective semiconductor materials,
are of great interest for modern and upcoming display technologies that
prioritize the light-emitting diodes (LEDs) with high efficiency and excellent
color purity. The prevailing approach to achieving efficient luminescence from
pervoskites is enhancing exciton binding effect and confining carriers by
reducing their dimensionality or grain size. However, splitting pervoskite
lattice into smaller ones generates abundant boundaries in solid films and
results in more surface trap states, needing exact passivation to suppress
trap-assisted nonradiative losses. Here, an ions-induced heteroepitaxial growth
method is employed to assembe perovskite lattices with different structures
into large-sized grains to produce lattice-anchored nanocomposites for
efficient LEDs with high color purity. This approach enables the nanocomposite
thin films, composed of three-dimensional (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, we demonstrate the perovskite LEDs 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 research
introduces a novel approach to the development of well-assembled nanocomposites
for perovskite LEDs, demonstrating high efficiency comparable to that of
state-of-the-art organic LEDs.
