The polypyrrole/n-Si structure has been directly formed onto the n-Si substrate by the electrochemical polimerization of the organic polypyrrole at 45 degreesC electrolyte temperature. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the structure have been determined at various temperatures in the range of 77-300 K and different frequencies. Some diode parameters have been calculated from these curves. It has been seen that the measured capacitance decreases with increasing frequency due to a continuous distribution of the interface states in the frequency range of 10 kHz-1 MHz. The barrier heights values obtained from the I-V and C-V characteristics have been compared. It has been seen that the barrier height value obtained from the C-V measurements are higher than that obtained from the I-V measurements at various temperatures. This behaviour has been attributed to the interfacial layer, the interface states and barrier inhomogeneity of the structure. Also this discrepancy can be due to the different nature of the C-V and I-V measurement techniques. A correlation seems to exist between the variation of the band gap and Fermi level energy of Si with temperature. (C) 2005 Elsevier Ltd. All rights reserved.