Highly Efficient Pure‐Red Quasi‐2D Perovskite Light‐Emitting Diodes Enabled by Propylammonium Chloride Passivator

Abstract Perovskite light‐emitting diodes (PeLEDs) based on quasi‐2D perovskites have attracted great attention in the past few years. Although significant achievements are made in device performance, fabrication of high‐efficiency PeLEDs with pure‐red (620–635 nm) light emission remains a significant challenge, which inhibits their practical application for full‐color displays. Herein, a series of efficient red PeLEDs at 625 nm are realized by employing volatile alkylammonium chlorides (propylammonium chloride) passivators. The interaction of PbI 2 with propylamine (PA) … H + Cl − in the precursor solution effectively passivates the defects, leading to reduced non‐radiative recombination and enhanced device performance. By optimizing the amount of PACl, an external quantum efficiency (EQE) of 16.1% and a maximum brightness of 1701 cd m −2 are achieved, among the best‐performing quasi‐2D I‐based PeLEDs with emissions ranging from 620 to 635 nm. This work provides a new route to improve the stability and efficiency of pure‐red PeLEDs.