A PV cell is the basic unit of a PV array. It is usually made of a silicon substrate coated with a thin film. These are mounted together with supporting structure to form PV panel. A number of technologies are available, but costs vary widely and increase sharply with high efficiencies.
Thin film technologies are generally less expensive than the others, as well as being lighter. Some versions have reached 23% efficiency
Single junction gallium arsenide up to 28% efficient
Multijunction cells, three and four junction cells have reached about 36% efficiency without concentrators and up to 46% with concentrators.
Crystalline silicon cells, 25-26 %, 22% for commercially available products (2019).
Emerging technologies: Perovskite cells may reach over 30% efficiency for very low costs. Still in development.
Multijunction cells are over 100 times more expensive than less efficient crystalline silicon cells or thin film cells
- G.D.J. Harper - Domestic solar energy: a guide for the home owner 2009. ISBN 978-1-84797-060-2 p. 140