Thin cadmium selenide layers were deposited by chemical bath deposition (CBD) on various substrates: glass, gold, indium tin oxide (ITO), and poly(3-methylthiophene) (PMeT), an organic conducting polymer. In all cases, CdSe adhered strongly to the substrate. X-ray diffraction, scanning electron microscopy, and optical transmission revealed an effect of the substrate nature upon the structural and optical properties of CdSe films. Because CdSe is an n-type semiconductor and PMeT either a p-type semiconductor or a quasi-metallic conductor, attention was focused on the hybrid organic-inorganic photovoltaic junctions, which result either from CdSe chemical bath deposition on PMeT or, conversely, from PMeT electropolymerization on CBD CdSe. In the former case, a p-n type junction was obtained, whereas, in the latter case, a Schottky-type junction was obtained. The nonoptimized photovoltaic energy conversion efficiency of these junctions under 56 mW cm(-2) white light from a Xenon lamp were 0.03 and 1.3%, respectively. When CdSe was deposited in the presence of silicotungstic acid (STA) in the chemical bath, localized energy levels were created in the forbidden band of CdSe, which improved the optical properties of the thin films, and hence, the energy conversion efficiency, which increased up to 2.7% for the Schottky-type photovoltaic organic-inorganic PMeT/CdSe(STA) photovoltaic junction.