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@INPROCEEDINGS{Jeangros:827179,
      author       = {Jeangros, Quentin and Duchamp, Martial and Werner,
                      Jérémie and Dunin-Borkowski, Rafal and Niesen, Björn and
                      Ballif, Christophe and Hessler-Wyser, Aïcha},
      title        = {{I}n situ {TEM} analysis of structural changes in
                      metal-halide perovskite solar cells under electrical bias},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01377},
      pages        = {804 - 805},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {Organic-inorganic metal-halide perovskite solar cells are
                      emerging as a promising photovoltaic technology to harvest
                      solar energy, with latest efficiencies now surpassing
                      $22\%1$ - an impressive increase from the first reported
                      value of $3\%$ in 2009.2 In addition to low manufacturing
                      costs, the optical properties of such cells can be tailored
                      to form efficient tandems when combined with high-efficiency
                      silicon solar cells.3 A typical perovskite cell structure as
                      investigated here is based on a methylammonium lead
                      trihalide absorber (MAPbI3) that is placed between hole-
                      (Spiro-OMeTAD) and electron-selective contacts (a
                      fullerene-based material).While new record efficiencies are
                      frequently reported, the commercial application of this
                      solar cell technology remains hindered by issues related to
                      thermal and operational stability. Different mechanisms that
                      are still debated modify cell properties with time,
                      temperature, illumination and general operating conditions.4
                      In order to correlate applied voltage (V) and resulting
                      current (I) to changes in active layer chemistry and
                      structure on the nanometre scale, we performed both ex situ
                      and in situ transmission electron microscopy (TEM)
                      experiments, involving (scanning) TEM (STEM) imaging,
                      selected-area electron diffraction, energy-dispersive X-ray
                      spectroscopy and electron energy-loss spectroscopy. Samples
                      were prepared by focused ion beam (FIB) milling, with
                      exposure to air during transfer to the TEM minimised to <5
                      minutes to reduce any degradation of MAPbI3.First, the
                      effects of exposure to air and electron beam irradiation
                      were assessed in relation to FIB final thinning parameters.
                      Once adequate sample preparation and observation conditions
                      were identified, changes in morphology during cell
                      characterisation were assessed ex situ by comparing lamellae
                      extracted from as-manufactured and tested cells and then in
                      situ by contacting FIB-prepared samples to a
                      microelectromechanical systems (MEMS) chip mounted in a TEM
                      specimen holder5 (Fig. 1a). Cell manufacturing parameters
                      led to iodine diffusion into the hole collector, with the
                      width of this diffused layer remaining constant during I-V
                      characterisation. Similarly to ex situ experiments, the
                      MAPbI3/Spiro interface was observed to delaminate during in
                      situ electrical measurements, resulting in the presence of a
                      ~5 nm Pb-rich layer on the hole-transparent-layer side
                      (Figs. 1b-c). In addition, PbI2 nanoparticles were observed
                      to nucleate within the MAPbI3 layer at the hole-collector
                      interface and at the positions of structural defects (Figs.
                      1b-d).Overall, the active MAPbI3 layer was observed to be
                      sensitive to sample preparation, exposure to air,
                      observation conditions and I-V stimulus, resulting in the
                      need for great care to deconvolute each effect. Different
                      mechanisms that may all contribute to the decrease in
                      efficiency of the cell were identified both ex situ and in
                      situ, including ionic migration, PbI2 formation and local
                      delamination of interfaces.},
      month         = {Aug},
      date          = {2016-08-28},
      organization  = {16th European Microscopy Congress (EMC
                       2016), Lyon (France), 28 Aug 2016 - 2
                       Sep 2016},
      cin          = {PGI-5 / ER-C-1},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)8 / PUB:(DE-HGF)7},
      doi          = {10.1002/9783527808465.EMC2016.6370},
      url          = {https://juser.fz-juelich.de/record/827179},
}