Surface and bulk phenomena in conjugated polymers devices

We report a number of investigations into a variety of surface and bulk phe nomena which are particularly relevant to the design of polymer optoelectro nic devices, and in particular to light-emitting diodes (LEDs). First, we c onsider the surface properties of the most common anode, a thin layer of in dium tin oxide (ITO), as modified by chemical and physical treatments. We s how how the treatments affect the electrode workfunction, surface energy, m orphology, sheet resistance and therefore, the LEDs efficiency and lifetime . We will also consider the effect of a conducting polymer hole-transport l ayer, such as poly(styrene sulfonate) doped poly(3,4-ethylene dioxythiophen e) (PEDOT), incorporated between the ITO and the active layer. Secondly, we turn our attention to the optimisation of the photoluminescence (PL) effic iency, and report examples of how the polymer microstructure and possibly t he engineering of disorder in a class of poly( p-phenylene vinylene)s and p oly- or oligo-thiophenes can determine a significant increase of the PL eff iciencies in the solid state. (C) 2000 Elsevier Science S.A. All rights res erved.