We have studied the transport properties of electron-and hole-dominated MEH-PPV, poly͑2-methoxy,5-͑2Ј-ethyl-hexoxy͒-p-phenylene vinylene͒, devices in the trap-free limit and have derived the temperature-dependent electron and hole mobilities (ϭ 0 e ␥ͱE) from the space-charge-limited behavior at high electric fields. Both the zero-field mobility 0 and electric-field coefficient ␥ are temperature dependent with an activation energy of the hole and electron mobility of 0.38Ϯ0.02 and 0.34Ϯ0.02 eV, respectively. At 300 K, we find a zero-field mobility 0 on the order of 1Ϯ0.5ϫ10 Ϫ7 cm 2 /V s and an electric-field coefficient ␥ of 4.8Ϯ0.3 ϫ10 Ϫ4 (m/V) 1/2 for holes. For electrons, we find a 0 an order of magnitude below that for holes but a larger ␥ of 7.8Ϯ0.5ϫ10 Ϫ4 (m/V) 1/2. Due to the stronger field dependence of the electron mobility, the electron and hole mobilities are comparable at working voltages in the trap-free limit, applicable to thin films of MEH-PPV.

An electroluminescent device comprising a transparent or translucent Support, a transparent or translucent first electrode, a Second conductive electrode and an electrolu minescent phosphor layer Sandwiched between the transpar ent or translucent first electrode and the Second conductive electrode, wherein the first and Second electrodes each comprises a polymer or copolymer of a 3,4dialkoxythiophene, which may be the Same or different, in which the two alkoxy groups may be the same or different or together represent an optionally Substituted oxy-alkylene oxy bridge; a display comprising the above-mentioned elec troluminescent device; a lamp comprising the above mentioned electroluminescent device; manufacturing processes for the above-mentioned electroluminescent devices, and the use of Such devices for the integrated backlighting of Static and dynamic posters and Signage.

We study the effect of blended and layered titanium dioxide (TiO 2) nanoparticles on charge transfer processes in conjugated polymer photovoltaics. A two order of magnitude increase in photoconductivity and sharp saturation is observed for layered versus blended structures, independent of the cathode work function. Using electrodes with similar work functions, we observe low dark currents and open circuit voltages of 0.7 V when a TiO 2 nanoparticle layer is self-assembled onto the indium-tin-oxide electrode. Our results for the layered morphologies are consistent with charge collection by exciton diffusion and dissociation at the TiO 2 interface.

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We demonstrate that mixing insulating oxide nanoparticles into electroluminescent polymer materials results in increased current densities, radiances, and power efficiencies in polymer light emitting diode devices. For low driving voltages, an order of magnitude increase in current density and light output is achieved with minimal loss in device lifetime. At 5 V, we achieve radiances of 10 000 cd/m 2 with external quantum efficiencies ϳ1% for nanoparticle/MEH-PPV composite films.