Heterocyclic aromatic amine-modified hole transport layer enables energy level regulation for enhanced performance of deep blue QLEDs

Quantum dots (QDs) exhibit great promise for next-generation displays, yet deep blue quantum dots light-emitting diodes [deep blue QLEDs, CIE (International Commission on illumination) y < 0.06] lag behind red and green counterparts due to energy level mismatches and imbalanced carrier mobility. In this work, 2-aminopyridine was employed at the interface between the hole transport layer and the emitting layer to construct stepwise energy level regulation. The mechanism was elucidated through density functional theory calculations, photophysical characterization, and surface morphology analysis. The modifier deepens the HOMO level of the hole transport layer from −5.75 to −5.97 eV and increases hole mobility from 4.08 × 10−7 to 1.56 × 10−6 cm2 V−1 s−1. The device based on the modified hole transport layer achieved a record external quantum efficiency of 23.16% in deep blue QLED (CIE y = 0.027). Interface modification demonstrates an effective approach to high-efficiency deep blue QLEDs and supports the commercialization of QLEDs.