Heterojunctions of porous silicon (PS) with polypyrrole (PPy) have been prepared and characterized. PS was formed by electrochemical anodization of p-type and n-type crystalline silicon (c-Si) wafers and PPy by electropolymerization of pyrrole. Current-voltage (I-P) characterizations of different PS/PPy structures were obtained in dark and under illumination. PPy forms a rectifying contact with PS layer on p-type c-Si substrate, but photovoltage was found in the heterojunctions of PPy on n-type c-Si with an open circuit of V(oc) = 135mV, a fill factor of FF = 0.25, a short circuit current density of J(sc) = 8.58 mA/cm(2) and an energy conversion efficiency of n(c) = 0.078%. However, when porous silicon powder is added between n-Si and PPy, the photovoltaic performance of this novel junction was significantly improved, giving V(oc) = 255 mV, J(sc) = 54.4 mA/cm(2), FF = 0.26 and n(c) = 1.8%. By fitting the I-V curves with the modified diode standard equation, the serial resistance of n-Si/PPy junction was about 10 K Omega and of 1 K Omega for n-Si/PS(powder)/PPy junction. (c) 2006 Elsevier B.V. All rights reserved.