Enhanced optoelectronic performance of blue quasi-2D perovskite light-emitting diodes enabled by diammonium-functionalized spacer

Blue perovskite light-emitting diodes (PeLEDs) have showcased remarkable potential for applications in vibrant color displays and solid-state lighting. Particularly, quasi-two-dimensional (quasi-2D) blue PeLEDs exhibit exceptional performance. However, conventional Ruddlesden-Popper (RP) phase quasi-2D perovskites suffer from low energy transfer efficiency and poor stability stemming from the van der Waals gaps between the perovskite layers, which hinder the preparation of high-performance quasi-2D blue PeLEDs. Here, we take advantage of the Dion-Jacobson (DJ) phase perovskite constructed with diammonium ligands to regulate the optical properties and structural stability of RP phase perovskite films. It is found that the mixed RP-DJ phase perovskites exhibit superior thermal stability, higher energy transfer efficiency and higher photoluminescence quantum yield (PLQY) compared to the pure RP phase perovskites. As a result, a sky-blue PeLED with an electroluminescence (EL) peak at 492.4 nm and a maximum external quantum efficiency (EQE) of 11.37 % was achieved.