The increasing demand for renewable energies has resulted in an exceptional growth of the solar and photovoltaic industry in recent years. In addition to wafer based collectors, thin film PV cells have especially gained in importance.
High purity silicon crystals are used to manufacture solar cells. The crystals are processed into solar cells using the melt and cast method. The cube-shaped casting is then cut into ingots, and then sliced into very thin wafers.
Processing wafers
Silicon atoms have four "arms." Under stable conditions, they become perfect insulators. By combining a small number of five-armed atoms (with a surplus electron), a negative charge will occur when sunlight (photons) hits the surplus electron. The electron is then discharged from the arm to move around freely. Silicon with these characteristics conducts electricity. This is called an n-type (negative) semiconductor, and is usually caused by having the silicon 'doped' with a phosphorous film.
In contrast, combining three-armed atoms that lack one electron results in a hole with an electron missing. The semiconductor will then carry a positive charge. This is called a p-type (positive) semiconductor, and is usually obtained when boron is doped into the silicon.
A p-n junction is formed by placing p-type and n-type semiconductors next to one another. The p-type, with one less electron, attracts the surplus electron from the n-type to stabilize itself. Thus the electricity is displaced and generates a flow of electrons, otherwise known as electricity.
When sunlight hits the semiconductor, an electron springs up and is attracted toward the n-type semiconductor. This causes more negatives in the n-type semiconductors and more positives in the p-type, thus generating a higher flow of electricity. This is the photovoltaic effect.
Okai sputtering targets developed rotatable and planar targets covers a wide range of coating materials used in thin film photovoltaic such as CIGS, a-Si, CdTe and wafer based cells.
Okai sputtering targets and arc cathodes for Wear Resistant Coating applications include:
✦ Aluminum - Al, 99.9%, 99.95%, 99.99%, 99.995%, 99.999%; rotatable target, planar target.
✦ Chromium - Cr , 99.5%, 99.8%, 99.9%, 99.95%; rotatable target, planar target.
✦ Molybdenum - Mo, 99.95%; rotatable target, planar target.
✦ Titanium - Ti, CP Grade 2 (99.2%), CP Grade 1 (99.7%), 99.9%, 99.95%, 99.99%, 99.995%, 99.999%; rotatable target, planar target.
✦ Silicon - Si, 99.9%, 99.95%, 99.99%, 99.995%, 99.999%; rotatable target, planar target.
✦ Silicon Aluminum - SiAl, 99.9%; 90:10, wt%; rotatable target.
✦ Tin Zinc - ZnSn, 99.99%; 50:50, wt%; rotatable target.
