S265 Solar 090829
Reference IH29-30 Solar Cell Types
OEES 265 Solar
| Crystalline silicon solar cells make up about 93% of the market share, and efficiencies of 11 to 16% have been achieved. Monocrystalline The first step in creating the silicon wafers for making these cells is to grow a high-purity, single-crystal silicon boule (ingot) that is several inches in diameter and several inches high. This boule is then sliced into wafers about 1/64" thick. Thus, each wafer consists of a single silicon crystal. The most efficient silicon cells are those made from such wafers. Multicrystalline Instead of starting with a single-crystal boule, manufacture of wafers for these cells begins with casting silicon into a block. Casting results in a large number of crystals being formed within the block. The block is then sliced into wafers. Multicrystalline solar cells are the ones most frequently being manufactured. |
| Several
materials are used to create cells of this type, and such cells are
often only about 0.001 millimeters thick. A lower cost than crystalline
silicon is one of their main advantages. Amorphous Silicon This is basically non-crystalline silicon that is deposited onto large sheets of glass or stainless steel. Amorphous silicon cells have efficiencies of 5 to 8%. This is less than that of crystalline silicon cells, but lower costs per watt can be achieved, even though the area needs to be larger than for crystalline cells. This technology is the most developed of the thin-film technologies. Cadmium-Telluride, Copper Indium Diselenide (CIS), Copper Indium Gallium Diselenide (CIGS), etc. Cadmium, tellurium, indium, selenium, and gallium are all chemical elements. Cadmium, copper, indium, and gallium are metals; tellurium is a metalloid (as is silicon) ; and selenium is a non-metal. Cells made from these materials appear to have some advantages over amorphous silicon. |
| Electrochemical solar cells use active
components that are liquid. One such type of cell uses nanocrystalline
titanium dioxide sandwiched between a front layer of tin-oxide-coated
glass sheet and a back layer of carbon with a glass or foil backing
sheet. The materials for these cells are cheap, but many challenges lie ahead in scaling up manufacturing processes for these cells. Efficiencies of 7% have been obtained. (Titanium dioxide is the most widely used white pigment for paints.) |