Vertical space charge limited device (VSCLD) driving an integrated quantum-dots light-emitting diode

Vertical light-emitting space charge limited device (V-LESCLD) is fabricated at low temperature using the cheapest solution process (spin-coating) and inorganic materials for the bottom driving device and for the light emitting layer. The device integrates a bottom space charge limited device (SCLD) and a top quantum dots light emitting diode (QLED). The new SCLD device is a three terminals device. Its structure is a stack of a bottom contact, a resistive low mobility layer, an ITO nanoparticles layer, a ZnO semiconducting layer and a top contact. The bottom contact acts as a gate. The intermediate ITO nanoparticles layer as a source and the top contact as a drain. The device has the same structure as Vertical Field Effect transistor (VFET). The main purpose to use this cheap spin-coated SCLD is that it can deliver more than 1 A cm -2 at low voltage, much more than any usual VFET, allowing the driving of the top QLED. Moreover, the very low subthreshold swing of 40 mV/dec over 5 drain current decades, probably due to a tunnel effect from ITO NPs to ZnO, allows fast driving of the QLED. Finally, and for the first time when using vertical electronic device, spin-coated ITO nanoparticles layer with some space between the nanoparticles is used as source. This layer covers much more the source area than any other nanowire-based layer. The V-LESCLD device achieves a low driving voltage of 1.9V in both gate and drain voltage driving modes, with a brightness of 11,300 cd m -2 and an on/off ratio of 10 6 at V GS = –6.5V and V DS = 9V.