We have developed modified poly(p-phenylene vinylene) (PPV) to improve its performance in organic electroluminescent devices. Encapsulated single-layer devices with this PPV on indium–tin oxide and a calcium cathode have been operated in air for>7000 hat 20 °C and>1100 hat 80 °C without noticeable degradation. Devices fabricated with this PPV, a conducting polymer layer as anode, and a sputtered low work-function alloy as cathode have efficiencies of over 2 lm/W, brightnesses of>600 Cd/m2at 4 V, and lifetimes of>1400 hdriven at∼100 Cd/m2initial brightness. ©1997 American Institute of Physics.