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Recent progress in amorphous and microcrystalline silicon based solar cell technology

: Rech, B.; Repmann, T.; Hüpkes, J.; Berginski, M.; Stiebig, H.; Beyer, W.; Sittinger, V.; Ruske, F.

20th European Photovoltaic Solar Energy Conference 2005. Proceedings : Barcelona, 6-10 June 2005
München: WIP-Renewable Energies, 2005
ISBN: 3-936338-19-1
European Photovoltaic Solar Energy Conference <20, 2005, Barcelona>
Fraunhofer IST ()
thin film; Si; ZnO

This contribution discusses recent scientific and technological challenges for the development of highly efficient amorphous (a-Si:H) and microcrystalline silicon (µc-Si:H) based thin film solar cells. Aluminium doped ZnO films prepared by sputtering and post deposition etching serve as transparent conductive oxide (TCO) material, which provide excellent light trapping properties. Challenges are the transfer of this approach to cost-effective reactive sputtering from metallic targets and the reduction of optical absorption losses in the front TCO films. We developed µc-Si:H solar cells by plasma-enhanced chemical vapour deposition (PECVD) using 13.56 MHz and 40.68 MHz excitation frequency in a process regime of high deposition pressures and high RF-powers. These conditions provide sufficiently "soft" deposition for the growth of high quality µc-Si:H material and yield high deposition rates. A stable aperture area module efficiency of 10.1 % was obtained for an a-Si:H/µc-Si:H module on 10x10 cm² substrate size. In case of the µc-Si:H PECVD process we discuss the questions of process stability, process reproducibility and up-scaling to large area production systems.