The optical and structural investigations of Zn-doped and undoped lead iodide thin films have been described. Zn-doped and undoped of lead iodide crystals have been grown by gel technique. The thin films were prepared by thermal evaporation of these grown crystals on glass substrates (80 degreesC). Perhaps, this should be the first time, to prepare the thin films of Zn-doped and undoped lead iodide crystals, as for our knowledge; as such reports are not available in the literatures. Measurements of the absorption coefficients in the range 1.6276-3.4361 eV is of the order of 10(5) cm(-1) for these films have been carried out. A careful analysis of the absorption coefficients indicated the crystalline character of the samples studied; a similar diagnosis was obtained from the X-ray and SEM analysis. The optical energy band gap decreases with increasing dopant concentrations. The absorption edge shifts towards the higher-wavelength side and becomes broader as the doping concentrations are increased. The samples are polycrystalline, and the crystallinity increases after doing but decreases when the thickness was taken above 3000 Angstrom. (C) 2002 Elsevier Science B.V. All rights reserved.