Efficient, single-layer molecular organic light-emitting diodes

The authors demonstrate efficient molecular organic light-emitting diodes that use direct hole injection from poly(3,4-ethylene-dioxythio-phene):poly(styrene-sulfonate) into a single layer of tris(8-hydroxyquinoline) aluminum (III) for carrier transport and electroluminescence. Single-layer devices have a lower operating bias and higher luminous power efficiency than conventional bilayer devices with a 4,4-bis[N-1-napthyl-N-phenyl-amino]biphenyl hole transport layer. The current density-voltage characteristics of single-layer devices follow Schottky-Richardson behavior and are consistent with an Ohmic contact at the anode.