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@ARTICLE{Gallet:865364,
      author       = {Gallet, Thibaut and Grabowski, David and Kirchartz, Thomas
                      and Redinger, Alex},
      title        = {{F}ermi-level pinning in methylammonium lead iodide
                      perovskites},
      journal      = {Nanoscale},
      volume       = {11},
      number       = {36},
      issn         = {2040-3372},
      address      = {Cambridge},
      publisher    = {RSC Publ.},
      reportid     = {FZJ-2019-04858},
      pages        = {16828 - 16836},
      year         = {2019},
      abstract     = {Hybrid organic inorganic perovskites are ideal candidates
                      for absorber layers in next generation thin film
                      photovoltaics. The polycrystalline nature of these layers
                      imposes substantial complications for the design of high
                      efficiency devices since the optoelectronic properties can
                      vary on the nanometre scale. Here we show via scanning
                      tunnelling microscopy and spectroscopy that different grains
                      and grain facets exhibit variations in the local density of
                      states. Modeling of the tunneling spectroscopy curves allows
                      us to quantify the density and fluctuations of surface
                      states and estimate the variations in workfunction on the
                      nanometre scale. The simulations corroborate that the high
                      number of surface states leads to Fermi-level pinning of the
                      methylammonium lead iodide surfaces. We do not observe a
                      variation of the local density of states at the grain
                      boundaries compared to the grain interior. These results are
                      in contrast to other reported SPM measurements in
                      literature. Our results show that most of the fluctuations
                      of the electrical properties in these polycrystalline
                      materials arise due to grain to grain variations and not due
                      to distinct electronic properties of the grain boundaries.
                      The measured workfunction changes at the different grains
                      result in local variations of the band alignment with the
                      carrier selective top contact and the varying number of
                      surface states influence the recombination activity in the
                      devices.},
      cin          = {IEK-5},
      ddc          = {600},
      cid          = {I:(DE-Juel1)IEK-5-20101013},
      pnm          = {121 - Solar cells of the next generation (POF3-121)},
      pid          = {G:(DE-HGF)POF3-121},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31475704},
      UT           = {WOS:000496763600012},
      doi          = {10.1039/C9NR02643F},
      url          = {https://juser.fz-juelich.de/record/865364},
}