Thallium(I) doped molybdenum heteropolyoxometalate (HPOM) thin films were prepared using simple chemical bath deposition technique. These HPOM thin films were characterized for their optoelectronic, structural, morphological and compositional properties using UV-vis spectra, electrical resistivity, thermo-emf, TGA-DTA, XRD, SEM-EDAX data. XRD studies of HPOM material shows that the material is polycrystalline and having simple cubic spinel structure. UV-vis spectroscopy revealed that, thallium(I) doped molybdenum HPOM is a direct gap semiconducting material having band gap 2.5 eV. The dc electrical resistivity and thermoelectric power was measured in the temperature range of 27-270 degrees C. The variation of resistivity with respect to temperature showed that there is negative resistance region in the temperature range of 160-263 degrees C, indicating semiconducting nature of HPOM material. The thermoelectric power for the sample was positive over the whole range of the temperature showing that the HPOM material is p-type semiconductor. Compositional analysis (EDAX) of samples shows the Tl(I) is intercalated in phosphomolybdate anion. The TGA-DTA data revealed that the molybdenum HPOM sample is thermally stable up to 286.04 degrees C. (C) 2008 Elsevier B.V. All rights reserved.