Structural, optical and electrical properties of polycrystalline Cu-In-Se films, such as CuInSe2 and ordered vacancy compounds (OVC), prepared by three-stage process of sequential chemical spray pyrolysis (CSP) of In-Se (first stage), Cu-Se (second stage) and In-Se (third stage) solutions have been studied in terms of substrate temperature at the second stage (T-S2). The films grown at T-S2 <= 420 degrees C exhibited larger grains in comparison with the Cu-In-Se films grown by the usual CSP method. Optical gap energy was approximately 1.06 eV for 360 degrees C <= T-S2 <= 420 degrees C, but increased dramatically from 1.06 to 1.35 eV when the T-S2 rose from 420 to 500 degrees C. Conductivity type was p-type for T-S2 < 420 degrees C, but n-type for T-S2 > 420 degrees C. (c) 2007 Elsevier B.V. All rights reserved.