Many potentially useful semiconducting materials for photovoltaic applications contain Group 14 elements in sulfides. Examples include Cu₂ZnSnS₄ (CZTS) and SnS which have been studied because they contain nontoxic elements that are relatively abundant on Earth. Describe the structures and properties of these sulfide materials and include a discussion of the sustainability of these Group 14 element-based materials in comparison with CdTe and CIGS (copper indium gallium sulfide).