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@INPROCEEDINGS{Schnohr:191843,
      author       = {Schnohr, Claudia and Eckner, S. and Kämmer, H. and
                      Steinbach, T. and Gnauck, M. and Johannes, A. and Kaufmann,
                      C. A. and Stephan, C. and Schorr, S.},
      title        = {{C}halcopyrite semiconductors: {A}tomic-scale structure and
                      band gap bowing},
      school       = {Univeristy of Jena},
      reportid     = {PUBDB-2014-04031},
      year         = {2014},
      abstract     = {Cu(In,Ga)Se2 is one of the most promising material systems
                      for thin film photovoltaics with record efficiencies above
                      $20\%$ on laboratory scale. The material crystallizes in the
                      chalcopyrite type crystal structure where the anion is
                      typically displaced from the ideal tetrahedral lattice site
                      due to the different properties of the neighbouring cations.
                      This subtle structural variation has a strong influence on
                      the energy band gap. Therefore, we have studied the
                      atomic-scale structure of Cu(In,Ga)Se2 as a function of
                      composition using extended X-ray absorption fine structure
                      spectroscopy and valence force field simulations [1]. The
                      element-specific In-Se, Ga-Se and Cu-Se bond lengths are
                      strikingly different from each other and remain close to the
                      values of the ternary parent compounds despite the
                      significant change of the lattice constants. The local
                      atomic arrangements thus deviate significantly from the
                      long-range crystallographic structure. Furthermore, the
                      material is characterised by structural inhomogeneity on the
                      atomic scale even if compositional fluctuations or secondary
                      phases are absent. Regarding the anion position, two
                      different displacement mechanisms have to be distinguished
                      both of which influence the nonlinear change of the band gap
                      with material composition. Similar results were also
                      obtained for Cu(In,Ga)S2 indicating that our findings
                      represent general features of these highly relevant yet
                      complex chalcopyrite semiconductors [2]. [1] C. S. Schnohr,
                      H. Kämmer, C. Stephan, S. Schorr, T. Steinbach, and J.
                      Rensberg, Phys. Rev. B 85, 245204 (2012).[2] S. Eckner, H.
                      Kämmer, T. Steinbach, M. Gnauck, A. Johannes, C. Stephan,
                      S. Schorr, and C. S. Schnohr, Appl. Phys. Lett. 103, 081905
                      (2013).},
      month         = {Mar},
      date          = {2014-03-17},
      organization  = {22rd Annual Conference of the German
                       Crystallographic Society, Berlin
                       (Germany), 17 Mar 2014 - 20 Mar 2014},
      cin          = {DOOR},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {DORIS Beamline C (POF2-54G13) / FS-Proposal: I-20110135
                      (I-20110135) / FS-Proposal: I-20100027 (I-20100027)},
      pid          = {G:(DE-H253)POF2-C-20130405 / G:(DE-H253)I-20110135 /
                      G:(DE-H253)I-20100027},
      experiment   = {EXP:(DE-H253)D-C-20150101},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://bib-pubdb1.desy.de/record/191843},
}