Crystalline Photovoltaic Materials

Crystalline Silicon

• 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)