Defect-Assisted Photoinduced Halide Segregation in Mixed-Halide Perovskite Thin Films

Solution-processable metal halide perovskites show immense promise for use in photovoltaics and other optoelectronic applications. The ability to tune their bandgap by alloying various halide anions (for example, in CH3NH3Pb­(I1–x Br x )3, 0 < x < 1) is however hampered by the reversible photoinduced formation of sub-bandgap emissive states. We find that ion segregation takes place via halide defects, resulting in iodide-rich low-bandgap regions close to the illuminated surface of the film. This segregation may be driven by the strong gradient in carrier generation rate through the thickness of these strongly absorbing materials. Once returned to the dark, entropically driven intermixing of halides…

• RS
  Royal Society
• RC
  Research Councils UK
• DO
  Department of Science and Technology, Ministry of Science and Technology, India
• EA
  Engineering and Physical Sciences Research Council

  Award: EP/M005143/1
• FN
  FP7 Nanosciences, Nanotechnologies, Materials and new Production Technologies

  Award: 604032