Vertically Concentrated Quantum Wells Enabling Highly Efficient Deep‐Blue Perovskite Light‐Emitting Diodes

Abstract

AbstractDeep‐blue perovskite light‐emitting diodes (PeLEDs) based on quasi‐two‐dimensional (quasi‐2D) systems exist heightened sensitivity to the domain distribution. The top‐down crystallization mode will lead to a vertical gradient distribution of quantum well (QW) structure, which is unfavorable for deep‐blue emission. Herein, a thermal gradient annealing treatment is proposed to address the polydispersity issue of vertical QWs in quasi‐2D perovskites. The formation of large‐n domains at the upper interface of the perovskite film can be effectively inhibited by introducing a low‐temperature source in the annealing process. Combined with the utilization of NaBr to inhibit the undesirable n=1 domain, a vertically concentrated QW structure is ultimately attained. As a result, the fabricated device delivers a narrow and stable deep‐blue emission at 458 nm with an impressive external quantum efficiency (EQE) of 5.82 %. Green and sky‐blue PeLEDs with remarkable EQE of 21.83 % and 17.51 % are also successfully achieved, respectively, by using the same strategy. The findings provide a universal strategy across the entire quasi‐2D perovskites, paving the way for future practical application of PeLEDs.