Implementation of highly stable microcrystalline silicon by VHFPECVD at high deposition rate in micromorph tandem cells

We have shown here the development of device quality microcrystalline materials with a wide range of growth rates varying in one order from a moderate deposition rate of 0.45nm/s to a considerable high deposition rate of 4.5nm/s. On the one hand, we have achieved a record high stabilized efficiency of 10% for microcrystalline silicon solar cells in a superstrate configuration at a deposition rate of 0.45nm/s, on the other hand, at a high deposition rate of 4.5nm/s we have shown a very promising stabilized efficiency of 6.7%. The monitoring tools to achieve such materials, such as in situ optical emission spectroscopy and a new parameter called "gas utilisation parameter" have been described. In this article we have reported results of the tandem "micromorph" cell with 11.4% stabilized efficiency using standard amorphous silicon (at a deposition rate of similar to 0.2nm/s) for the top cell. We also propose high deposition rate HWCVD proto-Si:H as a possible candidate for the top cell in combination with our high growth rate microcrystalline silicon bottom cell.