Photovoltaic technologies can also be categorized by the extent to which atoms bond with each other in individual crystals. As described by Bube (1998), there is a “family tree” of PVs based on the size of these crystals. The historically generic name “polycrystalline” can be broken down into the following more specific terms: (1) single crystal, the dominant silicon technology; (2) multicrystalline,in which the cell is made up of a number of relatively large areas of single crystal grains, each on the order of 1 mm to 10 cm in size, including multicrystalline silicon (mc-Si); (3) polycrystalline, with many grains having dimensions
on the order of 1µm to 1 mm, as is the case for cadmium telluride (CdTe) cells, copper indium diselenide (CuInSe2,) and polycrystalline, thin-film silicon;(4)microcrystallinecells with grain sizes less than 1µm; and (5)amorphous,in which there are no single-crystal regions, as in amorphous silicon (a-Si)