Novel spinel-type selenide semiconductor ZnSc₂Se₄ and its solid solution with sulfide for photovoltaics

It has recently been reported that the spinel-type sulfide (Zn,Mg)Sc₂S₄ possesses optoelectronic properties, including both n- and p-type dopability and strong visible-light emission. Herein, we present a novel isomorphic selenide, ZnSc₂Se₄, synthesized using a high-pressure synthesis technique, which exhibits n-type semiconducting behavior. Additionally, a solid solution between ZnSc₂S₄ and ZnSc₂Se₄ is realized over the entire composition range, enabling continuous tuning of the direct optical band gap from 2.07 to 1.35 eV (visible to near-infrared) by adjusting the S/Se ratio, accompanied by a sharp enhancement in electrical conductivity. These results revealed that the spinel-type chalcogenide system is a highly promising platform for photovoltaic absorbers. Furthermore, by substituting isovalent Mg [(Zn_1-zMg_z)Sc₂(S_1-xSe_x)₄], the band gap can be precisely controlled across nearly the entire visible region (2.86-1.35 eV), providing additional tunability for high-efficiency light-absorption and emission applications within the same host lattice.