Tailoring electron transport dynamics via dual-modulation for balanced charge injection in InP QLEDs

Interfacial defects and charge-transport imbalance at oxide electron transport layer (ETL)/quantum-dot interfaces remain key limitations in InP-based quantum-dot light-emitting diodes. Here, we present a dual-modulation strategy that combines ethanolamine (EA) ligand treatment with Mg-content control in ZnO-based ETLs to regulate their surface and electron-transport properties. EA attachment to ZnO nanoparticles was confirmed by Fourier transform infrared and XPS analyses. The treatment reduced oxygen-vacancy-related surface states, improved film uniformity, and lowered the surface work function, thereby facilitating electron injection. Within the same inverted device architecture, EA treatment increased the peak external quantum efficiency (EQE) from 4.08% for pristine-ZnO to 6.10% for EA-ZnO, corresponding to an improvement of approximately 50%. However, EA treatment also enhanced effective electron transport, which can intensify electron-dominant charge imbalance. Mg alloying was therefore introduced as an additional composition-dependent parameter to moderate electron transport while retaining the beneficial surface effects of EA modification. Adjusting the Mg content in EA-ZnMgO further increased the peak EQE to 9.23%, representing an additional improvement of approximately 51% relative to EA-ZnO. These results establish EA treatment and Mg-content adjustment as complementary and tunable approaches for adapting ZnO-based ETLs to the charge-injection requirements of different QD and hole-transport systems.