Amorphous Silicon Solar Cells

If you've ever used a solar-powered calculator, then you've used an amorphous silicon solar cell.

Conventional or bulk silicon solar cells are made by cutting thin wafers of silicon from a long cylindrical or square ingot. Silicon used for thin-films, including amorphous silicon (a-Si), is applied using a process called chemical vapor deposition (CVD). This has several advantages over the wafer sawing technique:

• a-Si can be deposited over large areas.
• a-Si can be deposited at low temperatures, which enables it to be deposited onto plastic rather than glass. This in turn allows for roll-to-roll processing and cell flexibility.
• Because of CVD and low temperatures, a-Si is much cheaper to produce than c-Si, and much less wasteful. It takes approximately one-tenth the silicon to create an amorphous silicon solar cell than it does a bulk silicon cell.

Amorphous silicon has a higher band gap than crystalline silicon, which means it absorbs visible light more readily than infrared light. Another thin-film Si application, called nanocrystalline silicon (nc-Si), has a band gap similar to crystalline silicon. This has inspired scientists to combine a-Si and nc-Si into one multi-junction (tandem) solar cell that can absorb a wider spectrum of sunlight, thus producing more electricity.

That is a brief look at the science behind amorphous silicon solar cells. The important points to take from this are cheaper production, lower overall cost and flexibility. For makers and buyers of a-Si solar cells, those advantages make up for the main disadvantage of a-Si cells (i.e. lower conversion efficiency).

a-Si solar cells are being developed for use in one of the more fascinating potential applications of building-integrated photovoltaics (BIPV). Researchers are developing semi-transparent solar cells that can be used as window glazing. In an odd twist, the cells would be part of both the active and passive solar design of a home. Passively, they would tint the window to block solar heat gain. Actively, they would produce electricity at the same time.

Monocrystalline Solar Cells / Amorphous Silicon Solar Cells / Gallium Arsenide Solar Cells / CIGS Solar Cells / Polycrystalline Solar Cells / Copper Indium Selenide Solar Cells