Abstract: A solar cell with improved energy conversion characteristics is formed from ordinary Czochralski or other types of silicon crystals that are sliced parallel to the growth axis or pulling direction. The slices are heat treated at a sufficiently high temperature and for a sufficiently long period of time to activate oxygen donor states in the slices. The heat treatment is of sufficient duration that at periodic maxima of oxygen concentration in the crystal it produces n-type regions where a background p-type dopant is overcompensated. Each n-type region thus formed is adjacent to a p-type region with a p-n junction therebetween. Collector contacts are applied at the faces of the slices to permit collection of carriers.