Investigation of the Defect-Tolerance of Chalcogenide Perovskites

Chalcogenide perovskites, such as BaZrS₃, have been proposed as defect-tolerant materials — that can maintain their electronic properties even in the presence of defects. When combined with their novel electronic structure, they have been proposed as promising materials for application in solar cells and optoelectronic devices; however, a systematic investigation of the defect tolerance of such perovskites is missing. We have used BaZrS₃ as a prototype chalcogenide perovskite and investigated its defect tolerance to intrinsic point defects using a combination of density-functional-theory calculations, spectroscopic and transport measurements. Based on the calculations, we find that most defects lead to shallow levels. However, we find that the sulfur vacancies have low formation energy. They lead to a deep transition level that is spatially localized to act as a non-radiative recombination center. Results of transport measurements with specimens annealed with S-rich and S-deficient conditions will be presented. Our work demonstrates that critical control over the chalcogen stoichiometry is necessary to improve the performance of these chalcogen perovskites.