Vertical Quasi-2D Perovskite on ZnMgO Enables High-Performance Pure-Red PeLEDs

Quasi-two-dimensional (quasi-2D) perovskites, featuring a large-cation-intercalated quantum-well structure, are efficient emitters for pure-red perovskite light-emitting diodes (PeLEDs); however, their electroluminescence is limited by poor carrier injection because all current quasi-2D emitters are horizontally aligned on low-mobility organic electron transport layers. Therefore, a PeLED with a quasi-2D perovskite vertically stacked on a high-mobility inorganic electron-transport layer is highly anticipated but has yet to be achieved. Here, we introduce branched guanidinium cations (GA⁺) and non-protonic phosphonium, (2-aminoethyl) triphenyl- cations (PAT⁺) to direct the vertical growth of quasi-2D emitters on a high-conductivity electron-transport layer, ZnMgO, enabling high-performance pure-red PeLEDs that exhibit a maximum luminance of 65 875 cd m^-2 and an external quantum efficiency of 14.63% even at a high brightness of 49 080 cd m^-2. Impressively, the low driving voltage, enabled by efficient carrier transport, also yields an operational half-lifetime of 5528 h at an initial luminance of 100 cd m^-2, which represents the most stable pure-red PeLED reported to date.