Phase-Pure Quasi-Two-Dimensional Layered Perovskites Enable Efficient Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) layered perovskites are widely employed in blue perovskite light-emitting diodes (PeLEDs) due to their ability to modulate energy transfer processes. However, the disordered stacking of inorganic and organic layers in the perovskite film forms multiple quantum well (QW) structures with irregular well-width distributions, leading to severe nonradiative recombination and limiting device efficiency. Here, we develop a synergistic bonding strategy in which the incorporation of diphenylmethylphosphonic acid (DMPA) facilitates the formation of coordination bonds (P-O-Pb) with the inorganic framework and hydrogen bonds (O···H-N) with the organic spacers. These interactions enable the formation of perovskite films with well-regulated QW distributions. Additionally, DMPA induces an upward shift in the perovskite energy level, thereby reducing the hole-injection barrier within the device. As a result, we achieve efficient blue PeLEDs with peak external quantum efficiencies of 23.2%, 22.0%, and 17.2% at emission wavelengths of 488, 480, and 472 nm, respectively.