In Situ Halide Insertion for Efficient and Stable Pure‐Red Perovskite Light‐Emitting Diodes

Abstract Substantial efforts have been made in boosting the performance of perovskite light‐emitting diodes (PeLEDs). However, there is still a tough challenge to achieve efficient and stable pure‐red PeLEDs with bromide‐iodine mixed quasi‐two‐dimensional (quasi‐2D) perovskite due to the unexpected halide migration under device operation. Here, the strategy of in‐situ halide insertion is proposed by dynamically treating quasi‐2D perovskite film with dodecyl dimethyl ammonium bromide (DDAB), which simultaneously suppresses the vacancy‐induced halide migration, inhibits the nonradiative recombination, and enlarges the perovskite bandgap for stable and efficient pure‐red emission. Meanwhile, a strong Coulombic force between DDAB and the perovskite is formed, which further anchors the halide for the suppression of halide migration. The merits of DDAB‐incorporated perovskites enable over 3‐fold enhancement in PeLED external quantum efficiency (EQE) from 2.25 to 8.16%. Furthermore, highly‐performed bromide‐iodine mixed pure‐red PeLEDs have been reported with a CIE coordinate of (0.707, 0.289), closely approaching the display standard Rec. 2020 (0.708, 0.292). More importantly, good operational and spectral stabilities without any shift of the electroluminescence (EL) spectra during operation have also been observed. Consequently, this work provides a feasible and effective approach for efficient and stable pure‐red PeLEDs.