Memory-Enabled Quantum-Dot Light-Emitting Diodes.

Quantum-dot light-emitting diodes (QLEDs) with memory capability can provide multifunctional integration properties in on-chip and intelligent electronic applications. Herein, memory properties are achieved by inserting a tungsten oxide (WO) film between the ZnO electron-transporting layer and cathode. Pentavalent tungsten ions (W) in this nonstoichiometric WO film can be oxidized to W by storing holes, inducing significant electrons in the adjacent ZnO layer. Hole storage in the WO layer suppresses electron injection into the quantum dot emissive layer, hence reducing electroluminescence intensity on the onset stage of the QLEDs. This operation-history correlation for the electroluminescence intensity means a memory behavior for the QLEDs. Furthermore, the power efficiency of the devices is greatly improved after inserting the WO layer due to electrical field-dependent self-adaptive electron injection into the quantum dots (QDs). We anticipate this type of QLEDs have potential applications in on-chip integration applications, such as the optical computing field and storage.