Preparation of microcrystalline silicon nip solar cells and amorphous-microcrystalline nipnip tandem solar cells entirely by hot-wire CVD

Recently, we reported on all-microcrystalline nip solar cells with all silicon layers prepared by hot-wire chemical vapour deposition (HWCVD), achieving initial and stable conversion efficiencies of eta = 5.4% (V-oc = 485 mV, j(sc) = 16.5 mA cm(-2), FF = 67.9%) for an i-layer thickness of 1.5 mu m on simple stainless steel substrates [M. Kupich, D. Grunsky, P. Kumar, B. Schroeder, Sol. Energy Mater. Sol. Cells 81 (2004) 141] [1]. These nip solar cells were found to be absolutely stable against light induced degradation. Furthermore, these microcrystalline nip structures were successfully incorporated for the first time into all-hot-wire amorphous-microcrystalline nipnip tandem solar cells. Initial conversion efficiencies up to eta = 7.0% on plain stainless steel substrates were obtained. These tandem structures showed only small SWE-like degradation. Further improvement of the solar cell performance, especially by the use of highly reflecting substrates with improved light trapping, is part of the ongoing work. First solar cells prepared on textured etched Ag/ZnO substrates provided by the IPV Juelich [O. Kluth, O. Vetterl, R. Carius, F. Finger, S. Wieder, B. Rech, H. Wagner, Mater. Res. Soc. Symp. Proc. 557 (1999) 731] [2] show increased initial efficiencies of eta = 5.6% for microcrystalline single junction nip solar cells and eta = 7.9% for "micromorph" nipnip tandem solar cells, due to higher current densities achievable by the enhanced light trapping. (c) 2005 Elsevier B.V. All rights reserved.