Growth of Thin <p> μc-Si:H on Intrinsic a-Si:H for <nip> Solar Cells Application

Abstract

The <p> μc-SiC:H / <i> a-Si:H junction can be considered to be a sub-system of a n/i/p solar cell. Optimised performance of this junction can be assumed to be a key feature for obtaining high efficiency solar cells. In this paper the authors present results on the conductivity of boron doped microcrystalline hydrogenated silicon (<p> μc-Si:H) thin films deposited on amorphous substrates (e.g. glass or glass/<i> a-Si:H). It is shown that, without any treatment of the substrate or of the underlying surface, the <p> layers showed a strongly reduced conductivity. This indicates either a bad nucleation or a poor microcrystalline behaviour. By using an appropriate surface treatment of the substrate, a gain in photoconductivity of about three orders of magnitude could be obtained (σ > 3 S/cm at a layer thickness of 400Å). We conclude from this, that for thin <p> type μc-Si:H layers the nucleation conditions are essential for obtaining best electric properties of the film w.r.t. solar cell performance. Based on these results, interface treatment was successfully implemented in n/i/p solar cells deposited on TCO coated glass and stainless steel. The results of these experiments are also presented.