Nanoshell-driven carrier engineering of large quantum dots enables ultra-stable and efficient LEDs

Quantum dot (QD) light-emitting diodes (QLEDs) have been considered one of the most promising candidates for nextgeneration lighting and displays. However, the suboptimal carrier dynamics at the interface between QDs and the hole transport layer (HTL), such as leakage and quenching induced by the accumulation of electrons at high brightness, severely deteriorates the device’s efficiency and stability. Here, we introduced the influence of carrier modulation by nanoshell engineering on the extermal quantum efficiency (EQE) and operation lifetime for QLEDs with large-sized QDs. The shell-driven engineering of energy level positions and band bending effectively eliminates the hole injection barrier and promotes charge injection balance. Photo-assisted Kelvin probe technique reveals that the ZnCdSe/ZnSeS QD/TFB (TFB = poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl))diphenylamine)) interface presents an increased surface potential and quasi-Fermi level splitting, reducing heat generation during device operation at high brightness. The shell-driven carrier engineering strategy reveals that our devices exhibit a high external quantum efficiency of 26.44% and an ultralong operation time (exceeding 50,000 h) to 95% of the initial luminance at 1000 cd/m² (T₉₅@1000 cd/m²). We anticipate that our results provide insights into resolving the issues at the QDHTL interface and demonstrate the importance of carrier management driven by QD nanostructure tailoring for the commercialization of QLEDs.