- Single-crystal silicon - Sliced from single-crystal boules of grown silicon,
these wafers/cells are now cut as thin as 200 microns. Research cells have
reached nearly 24-percent efficiency, with commercial modules of single-crystal
cells exceeding 15-percent.
- Polycrystalline silicon -
Sliced from blocks of cast silicon, these wafers/cells are both less
expensive to manufacture and less efficient than single-crystal silicon
cells. Research cells approach 18-percent efficiency, and commercial modules
approach 14-percent efficiency.
- Edge-defined film-fed growth ribbons -
Nearly single-crystal silicon ribbons grown from a crucible of molten
silicon, drawn by capillary action between the faces of a graphite die.
- Dendritic web - A film of
single-crystal silicon pulled from a crucible of molten silicon, like a soap
bubble, between two crystal dendrites.
Gallium Arsenide (GaAs)
A III-V semiconductor material from which high-efficiency photovoltaic cells are
made, often used in concentrator systems and space power systems. Research cell
efficiencies greater than 25 percent under 1-sun conditions, and nearly 28
percent under concentrated sunlight. Multijunction cells based on GaAs and
related III-V alloys have exceeded 30-percent efficiency. (reference)