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.