Quantum-Well Encapsulation Enabling Air-Processed Quasi-2D Perovskites with Long-Term Stability for Large-Area Deep-Blue Light-Emitting Diodes

Pure-bromide quasi-2D perovskites have achieved notable progress in enabling air-processed light-emitting diodes (PeLEDs). However, the ultrathin quantum well emitters are characteristic of high surface activity, leading to the deep-blue pure-bromide quasi-2D perovskite films still face challenges of long-term stability and optical tunability in ambient conditions. Here, a hydrolysis strategy is presented for achieving quantum well encapsulation, which enables significant enhancement in the stability and optical tunability of blue perovskite films, due to the hydrolysis of AlBr₃ or SiBr₄ generating oxo-bridged networks that passivate the surfaces of the quantum wells. The air-processed blue films exhibit an outstanding photoluminescence quantum yield of ≈50.9%, and remarkable color-stable-emission even after exposing in air (RH ≈10–20%, room temperature) for 2160 h, or under thermal stimuli (70 °C) for 92 h, which exceptionally exceeds the long-term stability of similar films fabricated in an inert environment. The deep-blue PeLEDs achieve a record external quantum efficiency of 4.02% for air-processed blue devices, which is comparable to the performance of analogous devices fabricated in a glove box. Notably, large-area deep-blue PeLEDs with an emission area of 9.0 cm² are presented, providing a promising path toward the development of high-performance, commercially viable perovskite display technologies.