Controlled modulation of charge storage and recombination in light-emitting diodes (LEDs) can function as an artificial memory platform, where charge storage mimics data writing, and recombination corresponds to data readout. Here we demonstrate hole storage lasting up to 0.8 s in an LED using the Cu-In-Zn-S quantum-dot (QD) emissive layer coupled with a deep-energy-level hole transport layer (HTL). Transient electroluminescence measurements reveal that the highly localized Cu-mediated hole states in QDs enable ultralong hole storage during device operation (data writing). By applying a reverse bias (data reading), delayed electroluminescence persisting for 0-0.8 s after voltage removal is observed. This phenomenon arises from the spatial confinement of holes within QDs and the reverse-bias-induced back transfer of electrons trapped in the HTL.
Zhu et al. (Tue,) studied this question.