Enhanced Hole‐Injecting Interface for High‐Performance Deep‐Blue Perovskite Light‐Emitting Diodes Using Dipole‐Controlled Self‐Assembled Monolayers

Abstract The Blue electroluminescence (EL) with high brightness and spectral stability is imperative for full‐color perovskite display technologies meeting the Rec. 2020 standard. However, deep‐blue perovskite light‐emitting diodes (PeLEDs) lag behind their green‐ or red‐emitting counterparts in brightness, quantum efficiency, and operational stability. Additionally, the Cl − /Br − mixed‐halide perovskites with wide bandgap typically designed for deep‐blue emitters are prone to degradation quickly under high operating bias due to low energy for halide migrations and vacancies formation, posing a significant challenge to spectral/operative stabilities. To address these issues, high‐performance deep‐blue PeLEDs are demonstrated by tuning the interface properties with Br‐2ETP, a self‐assembled monolayer (SAM) molecule engineered for a high dipole moment. The Br‐2EPT‐based hole‐injecting interface facilitates favorable energy level alignment between indium tin oxide and the deep‐lying valence band of the perovskite layer, suppressing the hole‐injecting barrier and non‐radiative charge recombination. Excellent perovskite film morphologies are observed at the top and buried surfaces by Br‐2EPT, improving the balance of carrier injection for light emission efficiency. Consequently, the devices exhibit deep‐blue electroluminescence at 457 nm, with an external quantum efficiency of 6.56% and spectral/operative stabilities.