| Autor: |
Okrepka H; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States., Ding Y; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States., Ghonge S; Department of Physics and Astronomy, University of Notre Dame, Notre Dame, Indiana 46556, United States.; Department of Chemistry and Physics, Saint Mary's College, Notre Dame, Indiana 46556, United States., Ruth A; Department of Physics and Astronomy, University of Notre Dame, Notre Dame, Indiana 46556, United States., Kuno M; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.; Department of Physics and Astronomy, University of Notre Dame, Notre Dame, Indiana 46556, United States. |
| Abstrakt: |
A thermodynamic band gap-based model for mixed-halide perovskite photosegregation currently explains numerous features of the phenomenon. This includes excitation intensity ( I exc ) thresholds for photosegregation as well as I exc -dependent photosegregation rates and rate constants. An intriguing prediction of the model involves I exc -dependent terminal halide stoichiometries ( x terminal ), following photosegregation. Rather than suggest a common terminal value, e.g., x terminal = 0.2, for methylammonium lead iodide/bromide [MAPb(I 1- x Br x ) 3 ], the model predicts I exc -dependent x terminal . This, in principle, allows for the controlled tuning of mixed-halide perovskite photoresponses. More important, though, is the opportunity to study this response to develop deeper insight into the origin of nearly ubiquitous photosegregation in lead-based, mixed-halide perovskites. Here, we demonstrate I exc -dependent x terminal in formamidinium/cesium, mixed-halide [FACsPb(I 1- x Br x ) 3 ] perovskites. We show that modifications to theory, which account for photosegregated domain subpopulations and photocarrier funneling efficiencies, lead to good agreement between measured and predicted I exc -dependent x terminal values. I-rich phase fractions increase with I exc and result in asymptotic x terminal versus I exc . This addresses an open discrepancy between experiment and theory to advance a detailed understanding of light-induced instabilities in mixed-halide perovskites. |
