Electroluminescence from phenylenevinylene-based polymer blends

The electroluminescent behaviour of films of poly(phenylphenylenevinylene) (PPPV), of PPPV blended with polystyrene (PS) and of PS doped with oligo(phenylenevinylene) sandwiched between indium–tin oxide (ITO) and Al contacts has been investigated. Polymer blending increases the relative quantum efficiency by up to two orders of magnitude. Studying the cell performance under application of rectangular voltage pulses as a function of temperature indicates that (i) hole injection at the ITO contact occurs by tunnelling, (ii) tunnel injection of electrons at the cathode is promoted by a space charge field across an interfacial Al₂O₃ layers and (iii) leakage of holes through the cathodic barrier is the main loss mechanism for holes.