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@INPROCEEDINGS{Bittkau:172723,
      author       = {Bittkau, Karsten and Hoffmann, Andre},
      title        = {{O}ptical simulation of photonic random textures for
                      thin-film solar cells},
      reportid     = {FZJ-2014-06167},
      year         = {2014},
      abstract     = {Many types of thin-film solar cell demand advanced
                      light-trapping concepts, in order to overcome the
                      limitations from the weak absorptance near the band gap.
                      Mostly, random textures are incorporated that scatters
                      incoming light diffusely prolonging the effective light path
                      in the absorber layer. As an alternative, periodic
                      structures like gratings or photonic crystals incorporated
                      at different interfaces of the device are investigated by
                      several groups. The optical design of optimized textures is
                      often done by rigorous optical simulations.We recently
                      demonstrated that a simple scalar approach sufficiently
                      describes angular resolved scattering in transmission and
                      reflection inside the absorber material. We found that pure
                      random textures scatter light most efficiently in reflection
                      at the back contact, whereas two-dimensional periodic
                      structures show their highest diffraction efficiencies in
                      transmission.We demonstrate that by the combination of both,
                      periodic structure and random texture conformally
                      incorporated at the front and back contact, the high
                      diffraction efficiency in transmission still dominates the
                      light scattering, but the resonance is much broader due to
                      the random structure. The light scattering at the back
                      contact still shows the broad angular distribution around
                      large angles like the random texture without periodic
                      structure. The combined photonic random texture, therefore,
                      benefits from both resulting in optimal transmission and
                      reflection properties.Starting with a randomly textured
                      ZnO:Al layer, that is well-known to provide high-efficiency
                      microcrystalline silicon solar cells, we add a
                      two-dimensional periodic structure with optimized period and
                      height on top of the random texture by applying the scalar
                      approach. The significant improvement of quantum efficiency
                      is verified by Finite-Difference Time-Domain simulations
                      taking into account real layer stack properties. The thus
                      optimized structure outperforms pure periodic and random
                      structures.},
      month         = {Apr},
      date          = {2014-04-14},
      organization  = {SPIE Photonics Europe, Brussels
                       (Belgium), 14 Apr 2014 - 17 Apr 2014},
      subtyp        = {Invited},
      cin          = {IEK-5},
      cid          = {I:(DE-Juel1)IEK-5-20101013},
      pnm          = {111 - Thin Film Photovoltaics (POF2-111)},
      pid          = {G:(DE-HGF)POF2-111},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/172723},
}