Improved Efficiency and Operational Lifetime in InP-Based Quantum-Dot Light-Emitting Diodes Using a ZnO:ZnS Nanocomposite Electron Transport Layer
Yisu Kim, Taesoo Lee, Beomsoo Chun, Jaekwon Kim, Jeonghun Kwak
Abstract
High Resolution Image Download MS PowerPoint Slide Quantum-dot (QD)-based light-emitting diodes (QLEDs) are widely recognized as promising next-generation display technologies due to their high efficiency, narrow emission bandwidths, and wide color gamut. However, conventional metal oxide-based electron transport layers (ETLs), such as those based on ZnO nanoparticles (NPs), suffer from intrinsic instability associated with oxygen vacancies. These defects often lead to charge imbalance, exciton quenching, and device degradation under electrical stress. To overcome these limitations, we incorporate wide band gap ZnS NPs with excellent optoelectronic properties, including high optical transparency, low defect density, and strong chemical stability, into ZnO NP-based ETLs in InP-based QLEDs. By optimizing the ZnS NP content, we successfully modulate the conduction band level, suppress exciton quenching at the ETL/QD interface, and achieve improved charge balance. As a result, InP-based QLEDs employing the ZnO:ZnS nanocomposite ETL exhibit a 1.7-fold increase in external quantum efficiency and a 1.8-fold improvement in power efficiency, along with a substantial reduction in efficiency roll-off. Furthermore, under electrical aging conditions, the nanocomposite ETL effectively mitigates electron overaccumulation and interfacial degradation, resulting in a 4.6-fold extension in operational lifetime. This work offers a practical and scalable approach to ETL engineering in QLEDs. It also provides new insights into the control of charge transport and exciton dynamics for the development of more stable and efficient optoelectronic devices.