Dual-Additives Balance Phase Distribution in All-Bromide Quasi-2D Perovskite for Spectrally Stable Pure-Blue Light-Emitting Diodes

Abstract

All-bromide quasi-two-dimensional (quasi-2D) perovskites exhibit remarkable potential for blue perovskite light-emitting diodes (PeLEDs) due to their superior optoelectronic properties. However, confining quasi-2D phases to n ≤ 3 and establishing an optimal gradient distribution for efficient carrier injection remain challenging. Herein, we present a dual-additives strategy, wherein 2-(4-fluorophenyl)ethylamine hydrobromide (p-F-PEABr) serves as a strong confinement additive that forms quasi-2D phases with n ≤ 3, while ethylammonium bromide (EABr) functions as a weak confinement additive that can disrupt the π-π stacking of p-F-PEABr and enable precise n-value modulation within the n ≤ 3 regime, consequently forming a gradient phase distribution. Therefore, through the dual-additives with strong and weak confinement, efficient energy transfer channels and smooth high-quality films are constructed, resulting in pure-blue (470 nm) PeLEDs with a maximum external quantum efficiency (EQE) of 4.26% and stable electroluminescence (EL) under operating voltages of 3-7 V without spectral shift. Notably, the Commission Internationale de l'Éclairage (CIE) coordinates of the EL are (0.138, 0.09), satisfying the National Television System Committee (NTSC) pure-blue standard with a negligible offset (Δ CIE is only (0.014, 0.005)) upon increasing the voltage to 7 V. This work provides a novel approach to develop spectrally stable pure-blue quasi-2D PeLEDs for wide colour gamut display applications.