Band structure modulation of chalcogenide perovskite with Eu as A-site cation

Chalcogenide perovskites with distorted structures, such as BaZrS3 and SrZrS3, are promising photovoltaic materials due to their high stability, strong absorption, and excellent electrical transport properties. Researchers have explored BaZr1-xTixS3 and BaZrS3-xSex alloys to reduce their band gaps, allowing them to absorb lower-energy photons. However, the hexagonal structures of BaTiS3 and BaZrSe3, along with the incompatibility of Ti or Se atoms in BaZrS3, lead to phase separation in these alloys. In this work, using EuZrS3 and Sr0.7Eu0.3ZrS3 alloys as examples, we demonstrate that the band structure of chalcogenide perovskites can be tuned by using Eu as the A-site cation. In EuZrS3, the Eu 4f orbitals contribute to the valence band maximum, thereby raising the valence band and resulting in a narrow bandgap of 0.54 eV. Furthermore, due to the structural and atomic compatibility of Eu with SrZrS3, the Sr1-xEuxZrS3 alloy is designed to fine-tune the band structures of both SrZrS3 and EuZrS3. EuZrS3 also exhibits typical semiconducting characteristics, making it promising for potential optoelectronic devices.