CsPb<sub>2</sub>Br<sub>5</sub> Plates/Quasi-2D Perovskite\nHeterojunction for Efficient Sky-Blue Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have gained\nsignificant\nattention owing to their remarkable tunability and color stability,\nand substantial progress has been made with green and red PeLEDs.\nHowever, the advancement of blue PeLEDs still lags far behind their\nred and green counterparts. In this study, we report efficient sky-blue\nPeLEDs utilizing an in situ fabricated CsPb<sub>2</sub>Br<sub>5</sub> plates/quasi-2D perovskite heterojunction using chelating molecules\nto modulate the crystallization process of perovskites. The wide bandgap\nof CsPb<sub>2</sub>Br<sub>5</sub> facilitated the formation of a type-I\nband alignment at the heterojunction, allowing efficient carrier transfer\nfrom CsPb<sub>2</sub>Br<sub>5</sub> to CsPbBr<sub>3</sub>. This heterojunction\nleads to a noteworthy enhancement of device efficiency. The PeLEDs\nexhibit a maximum brightness of 2311 cd m<sup>–2</sup>, accompanied\nby a maximum external quantum efficiency of 12.86% at 487 nm. Our\ntailored design of CsPb<sub>2</sub>Br<sub>5</sub>/perovskite heterojunction\nthin films offers a promising avenue for advancing PeLED performance.\nThis work contributes valuable insights into the burgeoning field\nof perovskite electroluminescence, paving the way for further optimization\nof PeLED technologies.