The window layer (p-layer) critically affects the conversion efficiency of a-Si:H based p-i-n type solar cells. This paper surveys possible alternative window materials in comparison with the standard boron doped a-SiC:H p-layer. A novel wide-gap amorphous silicon alloy, a-Si:F:H, will be shown to be a good alternative p-layer. As an example of nontraditional p-layer, boron based alloys (e.g., a-B:H) exhibit notable photovoltaic action in a-Si:H solar cells. We comment on attempts to deposit μc-Si alloy window layers on textured TCO-coated glass substrates.

No abstract

The validity of determining the defect density in a-Si:H and its alloys by integrating the sub-bandgap optical absorption coefficient is examined. It is shown that a formula derived for estimating Si-H bond density has been incorrectly applied to defect related absorption. In addition, the complex defect absorption processes have been oversimplified, by assumption, to the case of a single type of transition. Further, in practice, the defect absorption spectrum can not be unambiguously obtained at energies near and above the low end of the optical absorption edge. It is concluded that die integration method for quantitative defect density determination should be viewed at best as an empirical practice with considerable arbitrariness.