Linked from
The 23 pages that link to Solar cell, each with the reason it gives.
GermaniumRelated: Germanium serves as a substrate in some high-efficiency multijunction solar cells.
SeleniumRelated: Selenium was used in early photovoltaic cells before silicon became dominant.
GalliumRelated: Gallium-containing compounds are used in high-efficiency multijunction solar cells.
Indium tin oxideRelated: Transparent front electrodes in some solar cells use indium tin oxide.