In this work, we have investigated the structure of the thermally evaporated CdS thin films. The electrical characteristics, such as capacitance-voltage CV and current-voltage IV measurements, of identically prepared Al/n-CdS structure were studied. The values of barrier height and ionized trap like-donors concentration were obtained from the reverse bias capacitance-voltage CV measurements at 1 MHz under different temperatures in the range 303-403 K. The effect of different illumination intensities were also investigated. Current-voltage IV measurement indicates two conduction mechanisms: a conduction limited by thermionic emission TE at lower forward voltages and space charge limited conduction SCLC regime at higher forward voltages. A qualitative description of IV characteristics under different illumination intensities was done. The reverse biased IV measurement under illumination exhibited a high photosensitivity as compared to the forward one. The former was explained in terms of minority carrier injection phenomenon. The photovoltaic parameters, such as open circuit voltage and short circuit current, were obtained. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.