Rationalizing the light-induced phase separation of mixed halide organic–inorganic perovskites

, represent good candidates for low-cost, high efficiency photovoltaic, and light-emitting devices. Their band gaps can be tuned from 1.6 to 2.3 eV, by changing the halide anion identity. Unfortunately, mixed halide perovskites undergo phase separation under illumination. This leads to iodide- and bromide-rich domains along with corresponding changes to the material's optical/electrical response. Here, using combined spectroscopic measurements and theoretical modeling, we quantitatively rationalize all microscopic processes that occur during phase separation. Our model suggests that the driving force behind phase separation is the bandgap reduction of iodide-rich phases. It additionally explains observed…

• UD
  U.S. Department of Energy

  Awards: DE-FC02-04ER15533, FC02-04ER15533
• UO
  University of Notre Dame
• KA
  King Abdullah University of Science and Technology

  Award: OCRF-2014-CRG3-2268
• CO
  College of Science and Engineering, University of Minnesota
• BE
  Basic Energy Sciences

  Awards: DE-FC02-04ER15533, DE-SC0014334
• DO
  Division of Materials Sciences and Engineering