RESUMEN
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.
RESUMEN
Quasi-2D metal halide perovskites are promising candidates for light-emitting applications owing to their large exciton binding energy and strong quantum confinement effect. Usually, quasi-2D perovskites are composed of multiple phases with various numbers of layers (n) of metal halide octahedron sheets, enabling light emission from the lowest-bandgap phase by cascade energy transfer. However, the energy transfer processes are extremely sensitive to the phase distribution and trap density in the quasi-2D perovskite films, and the insufficient energy transfer between different-n phases and the defect-induced traps would result in nonradiative losses. Here, significantly reduced nonradiative losses in the quasi-2D perovskite films are achieved by tailoring the low-dimensional phase components and lowering the density of trap states. Butylammonium bromide (BABr) and potassium thiocyanate (KSCN) are employed to synergistically decrease the nonradiative recombination in the quasi-2D perovskite films of PEABr : CsPbBr3. The incorporation of BABr is found to suppress the formation of the n = 1 phase, while adding KSCN can further reduce the low-n phases, passivate the notorious defects and improve the alignment of the high-n phases. By incorporating appropriate contents of BABr and KSCN, the resultant quasi-2D perovskite films show high photoluminescence quantum yield (PLQY) and highly ordered crystal orientation, which enable not only the green light-emitting diodes (LEDs) with a high external quantum efficiency (EQE) of 16.3%, but also the amplified spontaneous emission (ASE) with a low threshold of 2.6 µJ cm-2. These findings provide a simple and effective strategy to develop high-quality quasi-2D perovskites for LED and laser applications.