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Title: Photo-induced halide redistribution in organic–inorganic perovskite films

Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced 'brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. In conclusion, our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6] ;  [5] ;  [1] ;  [7]
  1. Univ. of Washington, Seattle, WA (United States). Dept. of Chemistry
  2. Univ. of Lincoln, Lincoln (United Kingdom). School of Chemistry
  3. Univ. of Oxford, Oxford (United Kingdom). Dept. of Physics; Mathematical Inst., OCCAM
  4. Univ. of Washington, Seattle, WA (United States). Dept. of Bioengineering
  5. Univ. of Oxford, Oxford (United Kingdom). Dept. of Physics
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Research Laboratory of Electronics
  7. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Research Laboratory of Electronics; Cavendish Laboratory, Cambridge (United Kingdom)
Publication Date:
OSTI Identifier:
1282930
Grant/Contract Number:
SC0013957; SC0001088  
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States).
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE solar-cells; anomalous hysteresis; lead-iodide; single-crystals; thin-films; photoluminescence; CH3NH3PbI3; electron; diffusion; recombination