Field-induced light emission from a close-packed Mn-doped ZnS quantum-dot layer in an alternate-current thin-film electroluminescent configuration

By exploiting the configuration of an alternate-current thin-film electroluminescent device, we observe the emission of light from a close-packed spin-cast layer of manganese-doped zinc sulfide nanoparticles (NPs), sandwiched between two dielectric layers, induced by the application of an AC voltage. By means of a microwave-assisted polyol synthesis, we are able to obtain high-crystalline surfactant-free NPs, which can be closely packed in the emitting layer, allowing an emission mechanism due to local charge creation and transport, instead of the typical impact-excitation process. This synthesis route allows us to get rid of a bulk semiconductor layer, implying that far less expensive routes for the active layer deposition such as spin coating, inkjet printing, or spray coating can be used. Our work allows us to get a deeper insight into the role played by the NP structure on the charge-transfer mechanism behind light emission and paves the way to a new generation of non-toxic quantum-dot-based displays.