Expanding the Perovskite Periodic Table to Include Chalcogenide Alloys with Tunable Band Gap Spanning 1.5–1.9 eV

Optoelectronic technologies are based on families of semiconductor alloys. It is rare that a new semiconductor alloy family is developed to the point where epitaxial growth is possible; since the 1950s, this has happened approximately once per decade. Herein, this work demonstrates epitaxial thin film growth of semiconducting chalcogenide perovskite alloys in the Ba-Zr-S-Se system by gas-source molecular beam epitaxy (MBE).  This work stabilizes the full range y = 0 ? 3 of compositions BaZrS_(3-y)Se_y in the perovskite structure. The resulting films are environmentally stable and the direct band gap (E_g) varies strongly with Se content, as predicted by theory, with E_g = 1.9 ? 1.5 eV for y = 0 ? 3. This creates possibilities for visible and near-infrared (VIS–NIR) optoelectronics, solid-state lighting, and solar cells using chalcogenide perovskites.