Thin polycrystalline films of iron disulfide have been grown on different substrates by chemical vapor deposition. The films were characterized using optical absorption and TEM. RBS and EDAX analysis has been used to explore the chemical stoichiometry. XRD and FTIR allowed the identification of both FeS2 phases pyrite and marcasite. A novel method for sensitization of highly porous TiO2 electrodes with ultra thin (10 - 20 nm) polycrystalline films of FeS2 (pyrite) is presented. Photoelectrochemical solar cell using the above electrode generated high photovoltage of up to 600 mV compared with single crystalline electrode (200 mV). In this device the semiconductor with a small band gap and high absorption coefficient (FeS2 pyrite; EG = 0.9 eV; a = 6 × 105 cm-1) absorbs the light and injects electrons into the conduction band of the wide band gap semiconductor (TiO2 anatase; EG = 3.2 eV). Regeneration of holes is taking place by electron transfer from redox system in the electrolyte.