Rebirth of CuInS ₂ as hole transport material for perovskite solar cells

Copper indium sulfide, CuInS2 (CIS), has entered the field of photovoltaic cells for about three decades but somehow, they have not met their theoretically predicted efficiency as an absorber material. However, it is being employed a hole transport layer in conjunction with organic–inorganic perovskite solar cells, which offer improved environmental stability at reduced production cost. This commentary piece aims to draw researchers' attention use CIS layers organic-inorganic expectation that further study and improvements will propel into commercialization race.