Understanding the Electroluminescence Mechanism of CdSe/ZnS Quantum-Dot Light-Emitting Diodes With a Focus on Charge Carrier Behavior in Quantum-Dot Emissive Layers

We analyzed the electroluminescence (EL) mechanisms of quantum-dotlight-emitting diodes (QLEDs) with a focus on charge carrier trapping/detrapping. Multilayer quantum-dot (QD) emissive layers (EMLs) exhibit low void density and many QD surface traps, which provide high efficiency in the low bias voltage region; the efficiency gradually decreases in the high bias voltage region. The roles played by traps and charge carrier trapping/detrapping during QLED EL were revealed by transient EL and impedance spectroscopy analyses. Charge carrier trapping/detrapping of QLEDs with a multilayer QD EML in the low bias voltage region promoted charge injection, rapid initiation of EL, and high current efficiency. In contrast to the conventional view, traps improved QLED performance.