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@INPROCEEDINGS{Freter:1044268,
      author       = {Freter, Lars and Hsu, Hung-Chung and Sankar, Raman and
                      Chen, Chun- Wei and Dunin-Borkowski, Rafal and Ebert,
                      Philipp and Chiu, Ya-Ping and Schnedler, Michael},
      title        = {{I}mportance of {M}olecular {D}ipole {A}lignment and
                      {S}urface {C}ompensation in {P}-{V} {H}ysteresis of
                      {MAP}b{B}r3(001)},
      reportid     = {FZJ-2025-03138},
      year         = {2025},
      abstract     = {Metalorganic halide perovskites attracted extraordinary
                      attention as low-cost photovoltaic materials, due to their
                      rapid increase of the conversion efficiency within a few
                      years only. However, it is unclear to what degree the
                      reported conversion efficiencies extracted from current
                      density versus voltage (J-V) curves are accurate, since J-V
                      hystereses are known to make “bad cells look good”. It
                      is thus of paramount importance to unravel the physical
                      mechanisms inducing hysteresis, but no consent has been
                      achieved yet. We demonstrate the presence of a hysteresis in
                      tunneling spectra acquired at 4.3 K on cleaved MA-Br
                      terminated (001) surfaces of MAPbBr3 single crystals.
                      Simulations of the tunneling spectra reveal an underlying
                      polarization-voltage (P-V) hysteresis, caused by an
                      interplay of field-induced rotation and alignment of the MA
                      molecules, stabilized by dipole-dipole interactions, and an
                      ion-lattice relaxation. The field-induced, ferroelectric
                      polarization in the bulk is compensated at the surface by an
                      oppositely oriented, counteracting out-of-plane polarization
                      component of the otherwise in-plane antiferroelectrically
                      ordered surface dipole arrangement. This suggests that at
                      low temperatures only ferroelectric effects govern the
                      hysteresis in MAPbBr3 and its related compounds, whereas at
                      high temperatures thermally activated processes such as ion
                      migration and charge trapping-detrapping dominate},
      month         = {Jan},
      date          = {2025-01-19},
      organization  = {50th Conference on the Physics and
                       Chemistry of Surfaces and Interfaces,
                       Kona (USA), 19 Jan 2025 - 23 Jan 2025},
      subtyp        = {Other},
      cin          = {ER-C-1},
      cid          = {I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {5351 - Platform for Correlative, In Situ and Operando
                      Characterization (POF4-535) / DFG project
                      G:(GEPRIS)447951695 - Mikroskopische Untersuchung der
                      Umordnung von Molekül-Dipolen in
                      Organo-Metall-Halogenid-Perowskiten (447951695)},
      pid          = {G:(DE-HGF)POF4-5351 / G:(GEPRIS)447951695},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1044268},
}