Hydrogen ion implantations at an energy of 250keV and a dose of 3 x 10(16) cm(-2) were applied to float zone, Czochralski grown silicon wafers and to multicrystalline samples. It was found that after annealing at 350degreesC < T < 550degreesC for 1 h a n-p junction is formed and a photovoltaic behaviour is observed. Spectral responses show that the photocurrent in the near infrared part of the spectrum is comparable to that given by a standard silicon solar cell. The depth of the junction is about 2mum and C-V measurements show that the junction is graduated. Hydrogen plasma immersion leads to similar results. The conversion of p- to n-type silicon is explained by the formation of shallow donor levels associated to a high concentration of hydrogen. (C) 2002 Elsevier Science B.V. All rights reserved.