Polymer light-emitting diodes with polyethylene dioxythiophene–polystyrene sulfonate as the transparent anode

Polyethylene dioxythiophene–polystyrene sulfonate (PEDT–PSS) thin films spin-cast from aqueous dispersion have been used as semi-transparent anodes for polymer light-emitting diodes (LEDs). An external quantum efficiency of 2.0% was achieved with poly(2-methoxy,5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH–PPV), as the semiconducting luminescent polymer. LEDs fabricated with the PEDT–PSS anode exhibit an enhanced stress life in excess of 500 h at 70 mA/cm2 under constant-current conditions (initial brightness 600 cd/m2, reduced to 450 cd/m2 after 500 h).