Identifying Electronic Properties Relevant to Improving the Performance and Stability of Amorphous Silicon Based Mid-Gap and Low-Gap Cells: Final Subcontract Report, 16 January 1998-15 October 2001.
This report describes our experimental studies which have been concentrated in roughly five areas. Specifically: (1) We have examined a(question mark)Si:H grown very close to the microcrystalline phase boundary, so-called edge material, to help understand why such material is more stable with respect to light-induced degradation; (2) We have also studied the electronic properties, and degradation characteristics of mixed phase material that is mostly a(question mark)Si:H, but which contains a significant microcrystalline component; (3) We have examined the electronic properties of high deposition rate material. These studies have included both moderately high deposition rate material (up to 6/s) produced by the PECVD growth method, and extremely high deposition rate material (up to 130/s) produced by the HWCVD growth method. (4) We have examined series of a-Si,Ge:H alloys from several sources. In one extensive series of studies we examined low Ge fraction alloys in an attempt to learn more about the fundamentals of degradation in general. In a couple other studies we evaluated the properties of a-Si,Ge:H alloys produced by methods we had not previously examined. (5) Finally, for three different types of samples we compared basic material properties with companion cell performance data. This was carried out in each case on series of samples for which one or more specific deposition parameters were varied systematically.