Silicon foils, prepared by electrocatalysis, consist of microcrystalline, porous silicon. The size of the crystallites ranges between 15 and 20 nm, whereas the average pore size is about 60 nm. The density of this material is 65% of that of crystalline silicon. It is p-type and could be made n-type by neutron activation.Electrical and optical measurements indicate that the charge carrier mobility is limited by the grain boundaries.The grain boundaries give, in addition, rise to strong recombination of charge carriers. The luminescence of the material was investigated in a few experiments, and attempts were made to fabricate solar cells from electrocatalytically produced silicon foils with the pn-junctions prepared by neutron activation. The luminescence showed a peak at about 570 nin. The open circuit voltages obtained with solar cells were in the range between 120 aiid 200 mV. Further experiments to increase the intensity of the luminescence and to improve the quality of the cells could not be made within the framework of this project. It is, however, expected that further experimentation leads to a better understanding of the properties of the material and to applications.