Recent progress in quasi-two-dimensional and quantum dot perovskite light-emitting diodes harnessing the diverse effects of ligands: A review

Halide perovskites have been extensively studied for use as light-emitting diodes (LEDs) in next-generation displays due to their beneficial characteristics, including their high color purity and wide color gamut. Halide perovskites can be categorized into four representative structures: three-dimensional (3D) bulk, two-dimensional (2D), quasi-two-dimensional (quasi-2D), and quantum dot (QD). Recently, excellent advances in the performance of perovskite LEDs (PeLEDs), especially those with quasi-2D and QD architectures, have been demonstrated with the incorporation of organic chain ligands. Ligands can both modify the structure of PeLEDs, such as forming multi-quantum wells in quasi-2D PeLEDs and essential passivation layers in QD PeLEDs, and also enhance their optical performance. The appropriate use of ligands in PeLEDs can thus lead to greater luminescence, current efficiency, power efficiency, and external quantum efficiency. In this review, the principal roles of ligands in quasi-2D and QD PeLEDs are systematically summarized. Furthermore, current limitations and future perspectives are discussed in detail.