Steric Hindrance of Ligands Inhibits Interface Ion Penetration in Perovskite Nanocrystal-Based Electroluminescence Devices

Perovskite light-emitting diodes (PeLEDs) are critically limited by ion migration across interfaces, a process in which ions diffuse from the perovskite layer into adjacent charge-transport layers, leading to irreversible device degradation. In this study, we investigate the ion penetration behavior at different perovskite/charge-transport layer interfaces through interfacial action analysis and cross-sectional elemental mapping of the ionic distributions within PeLEDs. Our findings reveal that introducing steric hindrance at the perovskite/charge-transport layer interface effectively suppresses halide ion penetration into the device. The confinement of ions within perovskite nanocrystals enables peak external quantum efficiencies of 22.7% for pure blue emission (473 nm) and 27.8% for red emission (636 nm) in nanocrystal-based PeLEDs. Notably, the red PeLEDs exhibit a half-lifetime of 11.3 h at an initial luminance of 1000 cd m–2, underscoring the efficacy of the steric hindrance barrier in nanocrystal-based optoelectronics. This blocking strategy can also be applied to devices based on bulk perovskite films.