Method of making semicrystalline silicon article

A method of making a photovoltaic cell from a wafer of semicrystalline silicon having a surface adapted for the impingement of light thereon, said surface being formed from individual grains of silicon having a mean diameter of at least about 100 microns and grain boundaries that at said surface are in contact with or separated only slightly from the boundaries of adjoining grains, and a surface opposed to said impingement surface, comprising in a primary diffusion step, diffusing an impurity into said impingement surface of said wafer and then, in a secondary diffusion step, maintaining said wafer in an atmosphere substantially free from said impurity at a temperature and for a period of time sufficient to cause said impurity to penetrate between said grain boundaries and into said individual grains to form a photovoltaic junction at said impingement surface and extending across and below said surface and also into the interior of said wafer along and inwardly of said grain boundaries, said junction penetrating said wafer to a substantial depth whereby the total junction area exceeds the product of the linear dimensions of said wafer surface but not to an extent whereby said junction extends completely around the boundaries of said silicon grains or from said impingement surface to said opposed surface of said wafer.