Efficient flexible devices using a statistical copolymer of oxadiazole containing PPV

Flexible light-emitting diodes, with simple device architectures, fabricated using a random copolymer of hole transporting dialkoxy-substituted phenylenevinylene (PV) with an electron transporting oxadiazole containing PV derivative as the emissive layer and higher work function aluminum cathodes have been examined and compared with control devices on glass substrates. In all devices poly(3,4-ethylenedioxythiophene) with poly(styrenesulfonate) (PEDOT:PSS) was used as the hole injection layer and a thin layer of cesium fluoride or lithium fluoride has been used at the polymer/cathode interface to aid electron injection. Devices on plastic substrates with a lithium fluoride interlayer performed the best, exhibiting an average external quantum efficiency (EQE) of 0.8% and luminance of 1600 cd/m2 at 40 mA/cm2 (7.8 V). Stability of this device and morphology of the emissive film have also been investigated.