Trilayer hybrid polymer-quantum dot light-emitting diodes

We report a trilayer hybrid polymer-quantum-dot light-emitting diode fabricated by sandwiching a CdSe-ZnS core-shell quantum-dot (QD) layer, a few monolayers thick, between films of polyvinylcarbazole (PVK) and an oxadiazole derivative (butyl-PBD). All the layers have been deposited by a controlled spin-coating technique. Stable aqueous dispersion of QDs has been prepared to make possible the spin coating of multiple layers without affecting the layer underneath. Our device shows 20 times the quantum efficiency (0.2%) and less than half the threshold voltage (5 V) of a single-layer device made from the PVK-QD-PBD blend. This is attributed to balanced carrier conduction, enhanced recombination, and reduced quenching of emission due to a better electro-optical device design. (C) 2004 American Institute of Physics.