Transmission electron microscopy images show that the ZnO QDs are dominantly distributed at the circumference of the PVK polymer surface. Electroluminescence spectra for the hybrid polymer-QD WLEDs reveal a broad peak around 600 nm. The Commission Internationale de I'Eclairage chromaticity co-ordinates of the WLEDs fabricated utilizing hybrid polymer-QD WLEDs at 10 V are (0.39, 0.41), which is indicative of a white emission.

Luminescence mechanisms

The electrons and holes are accumulated at the ZnO QDs/PVK heterointerfaces due to the energy-band bending of ZnO QDs, resulting in the formation of the sub-bands between the ZnO QDs/PVK. Because the lifetime of the electrons existing in the ZnO/PVK heterointerface is much larger than that in the ZnO QDs, the light of the LED is emitted in the whole visible range due to continuous recombination between the electrons and the holes during the drop of the electrons from the conduction band to the valence band of the ZnO QDs. This results in the emission of white light because of the combination of the blue, green and red colours that are given out.

The luminescence mechanisms of the WLEDs are described on the basis of the experimental results and the energy band diagram. The device should benefit applications involving next-generation light sources.

The researchers presented their work in Nanotechnology.