A. Gawlik

Publications (5)17.26 Total impact

• Source

  Available from: Silke Christiansen

  Article: Stress and doping uniformity of laser crystallized amorphous silicon in thin film silicon solar cells

  R. M. B. Agaiby, M. Becker, S. B. Thapa, U. Urmoneit, A. Berger, A. Gawlik, G. Sarau, S. H. Christiansen
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  ABSTRACT: Simultaneous and locally resolved determination of the mechanical stress variation and the free hole concentration using Raman spectroscopy is demonstrated in laser crystallized amorphous silicon layers. Such layers are often used for the fabrication of thin film solar cells, e.g., on borosilicate glass substrates. The combined effects of stress and doping on the Raman signal can be separated based on the use of three wavelengths in the visible. The results show that the free hole concentration in the samples investigated varies between 1×10¹⁸ and 1.3×10¹⁹ cm ^-3 . Stress as well as the free hole concentration vary substantially within the sample. The stress level varies between 575 and 850 MPa (±12 MPa). Cross-sectional transmission electron microscopy images show the presence of extended lattice defects such as dislocations and grain boundaries in the crystallized Si layer which could account for the lateral stress variations detected by Raman spectroscopy. The impact of film inhomogeneity in terms of stress and doping on the performance of a solar cell will be discussed.
  Journal of Applied Physics 04/2010; · 2.17 Impact Factor
• Article: Silicon nanowire-based solar cells on glass: synthesis, optical properties, and cell parameters.

  V Sivakov, G Andrä, A Gawlik, A Berger, J Plentz, F Falk, S H Christiansen
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  ABSTRACT: Silicon nanowire (SiNW)-based solar cells on glass substrates have been fabricated by wet electroless chemical etching (using silver nitrate and hydrofluoric acid) of 2.7 microm multicrystalline p(+)nn(+) doped silicon layers thereby creating the nanowire structure. Low reflectance (<10%, at 300-800 nm) and a strong broadband optical absorption (>90% at 500 nm) have been measured. The highest open-circuit voltage (V(oc)) and short-circuit current density (J(sc)) for AM1.5 illumination were 450 mV and 40 mA/cm(2), respectively at a maximum power conversion efficiency of 4.4%.
  Nano Letters 04/2009; 9(4):1549-54. · 13.20 Impact Factor
• Conference Proceeding: Multicrystalline Silicon Thin Film Solar Cells Based on Laser Crystallized Layers on Glass

  G. Andra, J. Bergmann, A. Bochmann, F. Falk, A. Gawlik, E. Ose, J. Plentz, S. Dauwe, T. Kieliba
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  ABSTRACT: Multicrystalline silicon thin film cells were prepared by the LLC (layered laser crystallization) process on a glass superstrate. In this process an a-Si layer is crystallized by a cw laser resulting in a seed layer with grains exceeding 100 mum in size. Subsequently this seed layer is epitaxially thickened by simultaneous deposition of a-Si and crystallization by repeated pulses of an excimer laser. Then a phosphorus doped emitter is added. In this paper cells which are prepared by a single chamber PECVD laboratory type process are compared to devices prepared by an industrially relevant multi-chamber process based on high power diode laser crystallization and high rate electron beam evaporation, respectively. Crystallization with the diode laser resulted in significantly larger grains. However, solar cell performance does not quite reach the values of cells prepared by the laboratory process
  Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
• Source

  Available from: Pinar Dogan

  Article: CSG Minimodules using electron beam evaporated silicon

  R. Egan, M. Keevers, U. Schubert, T. Young, R. Evans, S. Partlin, M Wolf, J. Schneider, D. Hogg, B. Eggleston, M Green, F. Falk, A. Gawlik, G Andrä, M. Werner, C. Hagendorf, P. Dogan, T. Sontheimer, S. Gall
• Article: Microstructure and lattice bending in polycrystalline laser–crystallized silicon thin films for photovoltaic applications

  X. Maeder, C. Niederberger, S. Christiansen, A. Bochmann, G. Andrä, A. Gawlik, F. Falk, J. Michler
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  ABSTRACT: Grain size, grain boundary population, orientation distribution and lattice defects of polycrystalline silicon thin films are investigated by electron backscatter diffraction (EBSD). The silicon thin films are produced by a combination of diode laser melt-mediated crystallization of an amorphous silicon seed layer and epitaxial thickening of the seed layer by solid phase epitaxy (SPE). The combined laser-SPE process delivers grains exceeding several 10 μm of width and far larger than 100 μm in length. Strong lattice rotations between 10 and 50° from one side of the grain to the other are observed within the larger grains of the film. The misorientation axes are well aligned with the direction of movement of the laser. The intragranular misorientation is associated both with geometrically necessary dislocations and low angle boundaries, which can serve as recombination centres for electron-hole pairs. Since the lateral grain size is up to two orders of magnitude larger than the film thickness, the high dislocation density could become an important factor reducing the solar cell performance.
  Thin Solid Films 519(1):58-63. · 1.89 Impact Factor