The junction characteristics of the conducting polymer NpCIPh PPy [N-(p-chloro phenyl) polypyrrole] on a p-type Si substrate have been studied at room temperature. A direct optical band gap energy value of conducting polymer (NpCIPh PPy) was obtained as 2.94 eV. The ideality factor and barrier height of Al/NpCIPh PPy/p-Si/AI structure were determined from the forward current-voltage characteristics in the dark and were found to be 1.41 and 0.78 eV, respectively. The ideality factor and barrier height values for the Al/NpCIPh PPy/p-Si/AI structure are larger than that of conventional Al/p-Si Schottky diode. The contact parameters were calculated from Cheung's functions and modified Norde's function. The results found out from different methods were compared with each other. The barrier height value of 0.89 eV was obtained from capacitance-voltage characteristic. The different values of barrier height indicate the existence of barrier inhomogeneities. The conducting polymer (NpCIPh PPy) modifies the effective barrier height of conventional Al/p-Si Schottky diode as the organic film forms a physical barrier between Al metal and p-Si. (C) 2011 Elsevier B.V. All rights reserved.