Efficient InP-Based Quantum Dot Light-Emitting Diodes Using LiMgZnO Electron Transport Materials

It is well-known that metal ions (such as magnesium (Mg²⁺) and lithium (Li⁺) ions) are generally used to alleviate the problems of zinc oxide nanoparticles (ZnO NPs). Herein, the Mg²⁺ and Li⁺ ions are codoped into the ZnO NPs to simultaneously passivate the surface defects and tune the conduction band (CB) of NPs, which is confirmed by the spectra of X-ray photoelectron spectroscopy (XPS), electron spin resonance (EPR), and ultraviolet photoelectron spectroscopy (UPS). The LiMgZnO NPs can efficiently keep the excitons generated from the quantum dot (QD) emissive layer (EML) from being severely quenched and afford QD light-emitting diodes (QLEDs) with a balanced charge carrier. As a result, the use of LiMgZnO electron transport layer (ETL) achieves high-performance indium phosphide (InP)-based QLEDs with a luminance (L) of ∼7000 cd m^–2 at 6 V and a peak external quantum efficiency (EQE) of ∼12.0%, higher than those of devices made by the MgZnO ETL (L = ∼3300 cd m^–2 and EQE = 8.4%). Therefore, we believe that the LiMgZnO ETL can be used inside the InP-based QLEDs, affording its devices with improved performance.