Optimization of Low-Dimensional Components of Quasi-2D Perovskite Films for Deep-Blue Light-Emitting Diodes

Compared to efficient green and near-infrared light-emitting diodes (LEDs), less progress has been made on deep-blue perovskite LEDs. They suffer from inefficient domain [various number of PbX₆ ⁻ layers (n)] control, resulting in a series of unfavorable issues such as unstable color, multipeak profile, and poor fluorescence yield. Here, a strategy involving a delicate spacer modulation for quasi-2D perovskite films via an introduction of aromatic polyamine molecules into the perovskite precursor is reported. With low-dimensional component engineering, the n₁ domain, which shows nonradiative recombination and retarded exciton transfer, is significantly suppressed. Also, the n₃ domain, which represents the population of emission species, is remarkably increased. The optimized quasi-2D perovskite film presents blue emission from the n₃ domain (peak at 465 nm) with a photoluminescence quantum yield (PLQY) as high as 77%. It enables the corresponding perovskite LEDs to deliver stable deep-blue emission (CIE (0.145, 0.05)) with an external quantum efficiency (EQE) of 2.6%. The findings in this work provide further understanding on the structural and emission properties of quasi-2D perovskites, which pave a new route to design deep-blue-emissive perovskite materials.