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@ARTICLE{Astakhov:172018,
      author       = {Astakhov, O. and Smirnov, Vladimir and Carius, Reinhard and
                      Pieters, Bart and Petrusenko, Yuri and Borysenko, Valeriy
                      and Finger, F.},
      title        = {{R}elationship between absorber layer defect density and
                      performance of a-{S}i:{H} and µc-{S}i:{H} solar cells
                      studied over a wide range of defect densities generated by
                      2{M}e{V} electron bombardment},
      journal      = {Solar energy materials $\&$ solar cells},
      volume       = {129},
      issn         = {0927-0248},
      address      = {Amsterdam},
      publisher    = {North Holland},
      reportid     = {FZJ-2014-05567},
      pages        = {17 - 31},
      year         = {2014},
      abstract     = {We summarize an extensive study on the impact of absorber
                      layer defect density on the performance of amorphous
                      (a-Si:H) and microcrystalline (μc-Si:H) silicon solar
                      cells. To study the effects of the absorber layer defect
                      density we subjected set of a-Si:H and μc-Si:H cells to a 2
                      MeV electron bombardment. Subsequently the cells were
                      stepwise annealed to vary the defect density. The cells have
                      varying thicknesses and are illuminated from either the p-
                      or n-side. For reference we subjected i-layers to the same
                      treatment as the cells. The procedure enabled the reversible
                      increase of the i-layer defect density (NS) with two orders
                      of magnitude according to electron spin resonance
                      measurements (ESR) performed on reference samples. The large
                      variation of NS induces substantial changes in the
                      current–voltage characteristics (J–V) and the external
                      quantum efficiency spectra (EQE). These changes in device
                      characteristics provide a solid reference for analysis and
                      device simulations. It was found that performance of a-Si:H
                      cells degraded weakly upon NS increase up to 1017 cm−3 and
                      dropped steeply as defect density was increased further. In
                      contrast, performance of µc-Si:H cells showed continuous
                      reduction as NS raised. By comparing p- and n-side
                      illuminated cells we found that, for NS above 1017 cm−3,
                      the p-side illuminated a-Si:H cells outperformed the n-side
                      illuminated ones, however, the difference was barely visible
                      at NS below 1017 cm−3. On the contrary, the device
                      performance of n-side illuminated µc-Si:H cells was much
                      more affected by the increase in defect density, as compared
                      to the p-side illuminated cells. EQE results evidenced a
                      significant asymmetry in collection of electrons and holes
                      in µc-Si:H devices, where carrier collection was limited by
                      holes as defect density was increased. Based on the
                      experimental data we speculate that the improvement of
                      absorber material in terms of as-deposited defect density is
                      not of primary importance for the performance of a-Si:H
                      cells, whereas in μc-Si:H based solar cells, the reduction
                      of the absorber layer defect density below the
                      state-of-the-art levels, seems to improve the cell
                      performance.},
      cin          = {IEK-5},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IEK-5-20101013},
      pnm          = {111 - Thin Film Photovoltaics (POF2-111)},
      pid          = {G:(DE-HGF)POF2-111},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000342267400005},
      doi          = {10.1016/j.solmat.2013.12.024},
      url          = {https://juser.fz-juelich.de/record/172018},
}