Efficiency Enhancement of Tris(dimethylamino)-phosphine-Based Red Indium Phosphide Quantum-Dot Light-Emitting Diodes via Chlorine-Doped ZnMgO Electron Transport Layers

In this study, multishelled InP-based quantum dots (QDs) were synthesized using a phosphorus source tris(dimethylamino)phosphine [(DMA)3P] and were applied to solution-processed QD light-emitting diode (QLED) devices. (DMA)3P is not only a safe phosphorus source but is also a low-cost precursor for InP QDs. The quantum yield of the QDs increased from 71.0 to 81.8% by post-treatment with hexanethiol. The efficiency of the (DMA)3P-based red InP QLEDs was enhanced by using chlorine-doped ZnMgO (Cl-doped ZnMgO) nanoparticles (NPs) for the electron transport layer (ETL), which improved the charge balance in QLEDs. The energy barrier was reduced from 0.21 to 0.03 eV between the emitting layer and ETL with the Cl-doped ZnMgO NPs compared to that of the ZnMgO NPs ETL, and the electron injection barrier from the cathode to ETL increased as well. The maximum external quantum efficiency of the red InP-based QLEDs improved from 1.8 to 4.0% by Cl-doping the ZnMgO NPs. This is the highest device performance ever reported for QLEDs with (DMA)3P-based InP QDs. Employing the Cl-doped ZnMgO NPs for the ETL reduces the electron transport, balances the recombination of holes and electrons, and provides an efficient way of improving the charge balance in (DMA)3P-based InP QLEDs for low-cost electroluminescent devices.