The electrochemical deposition of polypyrrole (PPy) on p-Si(100) electrodes was investigated. The electrodeposition was performed in aqueous electrolyte solutions utilising cyclic voltammetry. Thin, adhesive, uniform PPy films were successfully deposited on p-Si(100) electrodes. The Si/PPy interface was characterised with infrared spectroscopic ellipsometry (IR-SE) and photoluminescence (PL) measurements to obtain information of a possible oxidation of the Si interface and charge carrier recombination at the interface, respectively. Very small amounts of interfacial silicon oxides have been found at the Si/PPy interface. PL measurements lead to the assumption that electrodeposition of PPy onto the Si electrodes generated only very few additional non-radiative recombination-active (nr) defects. Hence, polypyrrole is an excellent passivation of nr defects at the silicon surface. (C) 2008 Elsevier Ltd. All fights reserved.