YBi₂O_3.5+δSe_1-xCl_x: A family of semiconductors with a charge- and defect-tunable triple fluorite layer

Abstract: The design and development of new materials is crucial for advanced next-generation technologies, necessitating the modification of materials with tuneable atomic and electronic frameworks. This is often achieved by addition or replacement of metals and cations. Substitution of anions is also possible; here, we present the YBi₂O_3.5+δSe_1-xCl_x family which represent a new class of layered mixed anionic semiconductor materials with complete substitution of Cl by Se charge balanced by the introduction of oxide vacancies. The introduction of Se anions into the visible band gap material YBi₂O₄Cl shifts the band gap from 2.4 to 1.2 eV. This coupled Se/Cl substitution with O vacancy generation enables defect-engineered, tuneable new layered materials with tailored electronic properties in the visible band gap region, opening new pathways for development of semiconductors, thermoelectrics, and mixed oxide ion conductors