This thesis deals with photoelectron spectroscopy of conducting polymer systems. A particular system, poly(3,4-ethylenedioxythiophene) polystyrenesulfonic acid (PEDOT-PSS), has been the main focus of this work. It is an aqueous colloidal dispersion consisting of doped conjugated polymer PEDOT with counter ions provided by the PSS chains. PEDOT PSS films have previously proven to have a grain-like structure in which the grains have a ~30 Å thick insulating PSS outermost layer. The conductivity of thin PEDOT-PSS films has been improved through adding some high-boiling-point solvents to the PEDOT-PSS blend. With the help of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electron spectroscopy for chemical analysis based photon energy depth profiling (ESCAPEDEPF) measurements the reason for this increase has been explained. The major reason is a rearrangement of the morphology, in terms of an increase in the PEDOT to-PSS ratio in the surface region (i.e. the insulating PPS layer is decreased for each grain). The interface of PEDOT-PSS with aluminum (for contacting purposes) has also been studied with XPS and ultraviolet photoelectron spectroscopy (UPS). Due to the many components in the PEDOT-PSS film its reactions with aluminum was difficult to deduce. Therefore the aluminum interfaces with model molecules of each of the components of PEDOT-PSS were investigated to discern this. Phenyl capped EDOT-trimer was used as a model oligomer for neutral PEDOT. It has been shown that aluminum preferentially internets and forms covalent bonds with C-S carbons that causes a rearrangement of the charge density within the oligomer and breaks the n-conjugation. In PEDOT-PSS blends the PEDOT part is left intact and aluminum preferentially reacts with the SO-3 H+ and/or so-3 species of the PSS part. In order to deduce this the model systems PSSH, benzenesulfonic acid and sodium benzenesulfonate were studied. Sodium benzenesulfonate was used to model the PSS-Na+ contamination present in the polymer blend. The fact that aluminum does not internet with PEDOT avoids any break in the conjugation in the system, but it can however lead to dedoping of the PEDOT chains, therefore negatively affecting the mobility in the material and the charge transport across the PEDOT PSS/aluminum interface.