Organic Spacer Cation Engineering Enhances the Electroluminescence of Full-Color PeLEDs

Quasi-two-dimensional (quasi-2D) perovskites have great potential in pure-blue perovskite light-emitting diodes (PeLEDs). Nevertheless, disordered multi-n phase distribution gives rise to inhomogeneous quantum confinement, accompanied by high charge-transport barriers, which severely restrict the performance of pure-blue devices. This paper proposes a universal dual-functional modification strategy, which achieves efficient pure-blue PeLEDs by partially replacing phenethylammonium bromide (PEABr) with 2-methoxyethylammonium bromide (MOAmBr). Due to the smaller steric hindrance of MOAmBr and its strong interaction with the perovskite framework, it can effectively reduce the interlayer spacing of quasi-2D perovskites and regulate the distribution of phases, thereby enhancing quantum confinement and achieving a blueshift and high-purity electroluminescence (EL). At the same time, MOAmBr reduces the carrier injection barrier, improves charge migration, and inhibits internal recombination losses of the device. The optimized pure-blue PeLED achieves a peak external quantum efficiency (EQE) of 6.8% at 469 nm. Additionally, this universal strategy is successfully applied to green and red PeLEDs, achieving significant EQE values of 21.69 and 17.29% at 506 and 660 nm, respectively. This work provides a simple and versatile cation engineering method for constructing high-performance full-spectrum quasi-2D PeLEDs.