Hydrogenated amorphous silicon and silicon germanium triple-junction solar cells at high rate using RF and VHF glow discharges

We present our recent results on a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells made at high deposition rates using both RF and MVHF glow discharges. The growth parameters studied are under the constraints of manufacturing feasibility so that any improvement can be transferred to manufacturing lines. Using RF glow discharge, we achieved initial active-area efficiencies of 11.4% and 12.5% on Al/ZnO and Ag/ZnO back reflectors, respectively, at deposition rates of ∼4–6 Å/s. Similar initial cell efficiency were achieved at even higher deposition rates (∼6–8 Å/s) with MVHF glow discharge. Comparison studies of stability on these cells showed that the lightinduced degradations are ∼15% and ∼22% for a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells deposited with RF at ∼1 Å/s and ∼4–6 Å/s, respectively, while it is only 6–11% for the MVHF deposited triple-junction cells. The results demonstrate that VHF technology is desirable at high deposition rate in terms of increasing manufacturing throughput.