Self-assembled molecules enable robust interfaces for efficient and stable quantum dot light-emitting diodes

Colloidal quantum dot light-emitting diodes (QLEDs) are promising candidates for next-generation display technologies due to their narrow emission bandwidth, wavelength tunability, and solution processability. However, the device performance is severely limited by inefficient hole injection, primarily due to surface defects or energy-level misalignments, especially at the buried interface of the hole transport layer. Here, we employ a carbazole-based phosphonic acid, [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz), to modify the surface of nickel oxide (NiOx). MeO-2PACz is anchored to the NiOx surface via chemical interactions between its phosphonic acid groups and the NiOx, thereby enhancing interfacial adhesion and effectively passivating surface defects. Additionally, MeO-2PACz induces a downward shift in the NiOx energy level, reducing the hole injection barrier within the device. As a result, MeO-2PACz-treated QLEDs, emitting at 626 nm, exhibit a peak external quantum efficiency of 25.1%, a maximum luminance of nearly 65 000 cd m−2, and a T95 operational lifetime of over 385 000 h at an initial luminance of 100 cd m−2.