Simultaneous Low-Order Phase Suppression and Defect Passivation for Efficient and Stable Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskite is rising as a promising luminescent material for blue perovskite light-emitting diodes (PeLEDs). However, typical quasi-2D perovskites show a wide distribution of low-order phases and low efficiency owing to the inefficient energy transfer. Meanwhile, the defects and traps generated during the perovskite crystallization increase nonradiative recombination, further aggravating the external quantum efficiency (EQE). Herein, we demonstrate a unique quasi-2D perovskite with low-order phase suppression and defect passivation for efficient energy transfer and light emission by incorporating a 2D perovskite and an excess ammonium salt into the quasi-2D perovskite solution. By optimizing the new class of quasi-2D perovskite, we achieve blue PeLEDs with the brightness of 1765 cd m(-2), EQE of 7.51%, low turn-on voltage of 3.07 V, and long operation lifetime of 3961 s under constant driving current without any shift of the electroluminescence spectra. The work contributes to promoting efficient and stable blue PeLEDs.