THE POTENTIAL OF HOT-WIRE DEPOSITED MICROCRYSTALLINE SILICON FOR THIN FILM SILICON SINGLE- AND MULTI-JUNCTION SOLAR CELLS

摘要

In this paper, the potential of hot-wire chemical vapour-deposited μc-Si grown slightly away from the amorphous to microcrystalline transition, is explored in thin film nip-configured solar cells. A series of single junction cells with μc-Si i-layer thicknesses ranging from 0.5 to 3.0 μm was investigated. These cells were deposited onto stainless steel and did not comprise light-trapping elements. V{sub}(oc) was found to go down with increasing μc-Si thickness and has a highest value of 0.54 V for the thinnest sample. FF shows a maximum of 0.72 for the cell with the 1.0 μm i-layer. J{sub}(sc) and efficiency increase to nearly saturated values of 16.4 mA/cm{sup}2 and 5.2%, respectively. Annealing improves the cell performance, mainly by increasing FF. For proto-Si/μc-Si and μc-Si/μc-Si tandem cells good V{sub}(oc)-values of 1.38 and 1.04 V, and very high FF-values of 0.75 and 0.77 were obtained. A proto-Si/μc-Si/μc-Si triple junction cell had a V{sub}(oc) of 1.77 V and a FF of 0.69, which is lower than expected in view of the μc-Si/μc-Si tandem cell. This was found to be partly due to the top cell absorption. The good V{sub}(oc)- and FF-values for the single and multijunction cells and, in particular, the high FF-values of the tandem cells show the high optoelectronic quality and potential of our hot-wire μc-Si material.