Photovoltaic effect is observed in self-assembled heterojunctions obtained in p-type nanocrystalline Pb1-xFexS (x=0.25, 0.33, 0.50) films on n-type single crystal silicon substrates. The p-type ternary Pb1-xFexS films grown on these substrates by a solution growth technique were observed to be homogeneous and grow with basic lead sulfide structure. The lattice parameter of the nanocrystalline ternary films was observed to decrease with increase in x. The films were observed to have direct optical band gap from 1.90 to 1.60 eV as the iron concentration W increased from 0.25 to 0.50. The decrease in band gap with increase in iron concentration suggests the alloying of FeS (E-g = 0.04 eV) with the nanocrystalline PbS. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics confirmed the formation of heterojunctions in all the samples. Increase in the value of forward current and capacitance with increase in iron concentration (x) in the junctions can be attributed to the increase in surface area contact caused by decrease in the grain size of the films with x. (C) 2003 Elsevier B.V. All rights reserved.